Snort Deployment for NIDS (final)
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Questions and Answers

What is a limitation of Snort in regards to encrypted traffic?

  • It can check for intrusion by checking SSL Proxies
  • It cannot check for intrusion (correct)
  • It cannot detect SSL Proxies
  • It can decrypt encrypted traffic

    • What is the name of the program that can connect Snort to a database?

  • SnortDB
  • SensorConnect
  • Barnyard2 (correct)
  • Barnyard

    • Why might someone choose to use a Linux-based operating system for their Snort sensor?

  • Because Snort is only available on Linux
  • Because Linux is more user-friendly than Windows
  • Because Linux is more secure than Windows
  • Because the Windows version of Snort is no longer supported (correct)

    • What is an important consideration when choosing the base operating system for a Snort sensor?

    <p>Supportability</p> Signup and view all the answers

    What is one way to ensure the security of a Snort sensor?

    <p>Disable Unnecessary Services</p> Signup and view all the answers

    What is the purpose of Interface Pairing and SPAN in a Snort sensor?

    <p>To facilitate monitoring and detection</p> Signup and view all the answers

    What is a limitation of using open-source software like Snort?

    <p>Limited documentation and community support</p> Signup and view all the answers

    What is the primary function of a NIDS like Snort?

    <p>To detect and alert on potential intrusions</p> Signup and view all the answers

    Why is it recommended to not place a NIDS inline with network connections?

    <p>To prevent loss of network speed</p> Signup and view all the answers

    What is a Snort Sensor?

    <p>A NIDS placed in a network topology</p> Signup and view all the answers

    Why is it important to prioritize which systems to watch with a NIDS?

    <p>Because it's impossible to watch all systems and connections</p> Signup and view all the answers

    What is the purpose of a SPAN port on Cisco hardware?

    <p>To output all information on a single port</p> Signup and view all the answers

    What is a limitation of using modern switches with a NIDS?

    <p>They do not allow promiscuous mode by default</p> Signup and view all the answers

    Why is it recommended to use a hub to create a listening point in a network?

    <p>It allows promiscuous mode</p> Signup and view all the answers

    What is the benefit of using Cisco hardware with Snort?

    <p>Snort is built into many Cisco devices, making it easier to setup a Snort sensor</p> Signup and view all the answers

    What is the purpose of manual user intervention in a NIDS like Snort?

    <p>To stop an intrusion from continuing</p> Signup and view all the answers

    What is a crucial step in deploying Snort effectively?

    <p>Creating rules for Snort to function properly</p> Signup and view all the answers

    Why is Snort not a plug and watch solution?

    <p>Because it requires constant monitoring and troubleshooting</p> Signup and view all the answers

    What is the primary purpose of a NIDS like Snort?

    <p>To detect and respond to threats</p> Signup and view all the answers

    Why is it important to have a plan in place when using a NIDS like Snort?

    <p>To respond appropriately to identified attacks</p> Signup and view all the answers

    What should Snort be used in conjunction with?

    <p>Other security systems</p> Signup and view all the answers

    What is a limitation of Snort?

    <p>It does not provide comprehensive security</p> Signup and view all the answers

    Why are there commented out rules in the community rules?

    <p>Because they are not commonly needed rules and can be skipped.</p> Signup and view all the answers

    What is the purpose of community rules?

    <p>To provide alerting for common exploits that exist in networks.</p> Signup and view all the answers

    Why are not all active rules needed?

    <p>Because the rules that are active by default are the suggested rules to run on what is considered to be the most common network structure.</p> Signup and view all the answers

    What is the purpose of commenting out rules in community rules?

    <p>To leave them in the community rules in case the cyber security professional needs to use those rules.</p> Signup and view all the answers

    What should you do before implementing community rules?

    <p>Read the messages to get a better understanding of the purpose of the rule.</p> Signup and view all the answers

    Why are some rules not commonly used?

    <p>Because they are not needed for most networks.</p> Signup and view all the answers

    What is the purpose of the Attack-response.rules set?

    <p>To detect when a host is sending known responses to a successful attack</p> Signup and view all the answers

    Where can you download rules from the Snort.org Rule set?

    <p><a href="https://www.snort.org/downloads/#rule-downloads">https://www.snort.org/downloads/#rule-downloads</a></p> Signup and view all the answers

    What is the purpose of the Ddos.rules set?

    <p>To alert on traffic known for use in distributed denial of service attacks</p> Signup and view all the answers

    What is the purpose of the Experimental.rules set?

    <p>To include new type of rules</p> Signup and view all the answers

    What command is used to extract the rules from the Snort.org Rule set?

    <p>tar -xf</p> Signup and view all the answers

    What is the purpose of the Deleted.rules set?

    <p>To store old rules</p> Signup and view all the answers

    What is the purpose of the icmp-info.rules file?

    <p>Used when troubleshooting ICMP issues</p> Signup and view all the answers

    Which of the following rule categories is disabled by default and used to detect traffic sent from peer to peer services?

    <p>p2p.rules</p> Signup and view all the answers

    What is the minimum requirement for a Snort rule?

    <p>The sid option</p> Signup and view all the answers

    What is the purpose of the info.rules file?

    <p>Alerting on normal traffic found on a healthy, secure network</p> Signup and view all the answers

    What is the purpose of the rpc.rules file?

    <p>Alerting on known attacks against RPC services</p> Signup and view all the answers

    What is the purpose of the local.rules file?

    <p>Holding all custom rules created</p> Signup and view all the answers

    What is the purpose of the web-iis.rules file?

    <p>Alerting on known attacks against Microsoft Internet Information Server services</p> Signup and view all the answers

    What is the purpose of the imap.rules file?

    <p>Alerting on known attacks against IMAP email services</p> Signup and view all the answers

    What is the purpose of the misc.rules file?

    <p>Holding rules that are not included in other categories</p> Signup and view all the answers

    What is the purpose of the smtp.rules file?

    <p>Alerting on known attacks against SMTP mail services</p> Signup and view all the answers

    What is the purpose of the Backdoor.rules set?

    <p>To detect traffic generated by a backdoor network connection</p> Signup and view all the answers

    What is the purpose of the Bad-traffic.rules set?

    <p>To watch for illegal packet header settings</p> Signup and view all the answers

    What is the purpose of the Dns.rules set?

    <p>To alert on attacks against DNS services</p> Signup and view all the answers

    Where can you download rules from the Snort.org Rule set?

    <p><a href="https://www.snort.org/downloads/#rule-downloads">https://www.snort.org/downloads/#rule-downloads</a></p> Signup and view all the answers

    What is the purpose of the Experimental.rules set?

    <p>This is where new type of rules are included</p> Signup and view all the answers

    What command is used to extract the rules from the Snort.org Rule set?

    <p>tar -xf</p> Signup and view all the answers

    What is the main purpose of the icmp-info.rules file?

    <p>To troubleshoot icmp issues</p> Signup and view all the answers

    What is the minimum requirement for a Snort rule?

    <p>The 'sid' option only</p> Signup and view all the answers

    What does the 'Activate' rule action do?

    <p>Alerts then activates a dynamic rule</p> Signup and view all the answers

    What is the purpose of the p2p.rules file?

    <p>To detect traffic sent from peer to peer services</p> Signup and view all the answers

    What is the purpose of the oracle.rules file?

    <p>To detect known attacks against oracle database servers</p> Signup and view all the answers

    What does the 'Pass' rule action do?

    <p>Ignores or drops the packet</p> Signup and view all the answers

    What is the purpose of the web-misc.rules file?

    <p>To detect known attacks against common web attacks</p> Signup and view all the answers

    What is the purpose of the rpc.rules file?

    <p>To detect known attacks against RPC services</p> Signup and view all the answers

    What is the purpose of the sql.rules file?

    <p>To detect known attacks against MSSQL database servers</p> Signup and view all the answers

    What is the purpose of the local.rules file?

    <p>To hold all custom rules created</p> Signup and view all the answers

    What is the first step in writing your first snort rule?

    <p>Navigate to the /etc/snort/rules folder</p> Signup and view all the answers

    What is the purpose of the rule 'alert icmp any any any (msg:"ICMP detected";sid: 10001)'?

    <p>To detect ping requests</p> Signup and view all the answers

    How do you test your snort rule after creating it?

    <p>By sending 5 packets to google.com using the ping command</p> Signup and view all the answers

    What command is used to start Snort in console mode?

    <p>sudo snort -A console -c snort.conf</p> Signup and view all the answers

    What do you need to do to the community.rules file in snort.conf?

    <p>Comment it out</p> Signup and view all the answers

    What is the minimum requirement for a Snort rule?

    <p>An action and a protocol</p> Signup and view all the answers

    What is the purpose of the provided Python script?

    <p>To test and validate TCP and UDP rules</p> Signup and view all the answers

    What command can be used to verify the Python version?

    <p>python --version</p> Signup and view all the answers

    How many values are required to run a TCP packet test using the Python script?

    <p>2</p> Signup and view all the answers

    What is the recommended Python version to use with the script?

    <p>2.7.5</p> Signup and view all the answers

    How do you start the Python script?

    <p>By running <code>python checkrule.py</code></p> Signup and view all the answers

    What type of protocol transactions can the Python script generate?

    <p>Both TCP and UDP</p> Signup and view all the answers

    What type of IP should be entered for IP/URL in a TCP call?

    <p>IPv4</p> Signup and view all the answers

    What happens if no open port is found at the entered IP/URL?

    <p>The program will timeout after 1 minute</p> Signup and view all the answers

    What is the purpose of running checkrule.py?

    <p>To test each rule individually</p> Signup and view all the answers

    How many values need to be entered for a UDP packet call test?

    <p>3</p> Signup and view all the answers

    What is the consequence of not testing each rule individually?

    <p>You may be testing the wrong rule</p> Signup and view all the answers

    What is not required to be entered in the URL for a TCP call?

    <p>HTTP or HTTPS</p> Signup and view all the answers

    What is the primary purpose of checking the flag in a TCP rule?

    <p>To filter the rule to only capture packets that are ACK</p> Signup and view all the answers

    What is the result of not specifying the flag in a TCP rule?

    <p>The rule will alert or log every transaction between the source and host</p> Signup and view all the answers

    What type of communication is captured by a basic TCP rule without a filter?

    <p>Any communication that is sent or received via TCP protocol</p> Signup and view all the answers

    Why are the rules being written against outgoing packets?

    <p>To test the rule against outgoing packets, so you don't have to configure an additional Virtual Machine (VM) to test your rules</p> Signup and view all the answers

    What is the purpose of a TCP rule?

    <p>To alert or log connection-oriented communications between a source and destination</p> Signup and view all the answers

    How many transactions occurred in the example of the TCP rule without a filter?

    <p>Seven transactions</p> Signup and view all the answers

    What is the purpose of applying a filter to a TCP rule?

    <p>To eliminate false positives and reduce the number of alerts</p> Signup and view all the answers

    What is the main difference between a UDP rule and a TCP rule?

    <p>UDP rules are connection-less protocols, unlike TCP rules</p> Signup and view all the answers

    What is the purpose of the 'content' option in a UDP rule?

    <p>To filter out specific UDP transactions based on content</p> Signup and view all the answers

    What is the purpose of the 'revision' option in a rule?

    <p>To mark the version of the rule</p> Signup and view all the answers

    What is the purpose of the 'nocase' option in a rule?

    <p>To make the uricontent and content options case-insensitive</p> Signup and view all the answers

    What is the purpose of the 'session' option in a rule?

    <p>To capture TCP session information</p> Signup and view all the answers

    What is the purpose of the 'stateless' option in a rule?

    <p>To send an alert once the TCP session is completed</p> Signup and view all the answers

    What is the result of applying a filter to a TCP rule?

    <p>Fewer alerts are generated</p> Signup and view all the answers

    What is the benefit of using options in a rule?

    <p>To eliminate false positives and reduce the number of alerts</p> Signup and view all the answers

    What is the purpose of creating a basic TCP rule with an applied filter?

    <p>To eliminate false positives and reduce the number of alerts</p> Signup and view all the answers

    What is the primary function of Session Interception in an Intrusion Prevention System (IPS)?

    <p>Terminating TCP connections by sending a reset packet</p> Signup and view all the answers

    What is the risk associated with IPS identification?

    <p>Exploit beating the attempted block</p> Signup and view all the answers

    What is the purpose of the flexresp plugin in Snort?

    <p>To allow Snort to act as a session interception IPS</p> Signup and view all the answers

    What is the primary function of Gateway Intrusion Detection in Snort?

    <p>Blocking hostile traffic using Snort Inline</p> Signup and view all the answers

    What is the risk associated with altering access lists in Snort?

    <p>Self-inflicted Denial of Service</p> Signup and view all the answers

    What is the primary function of SnortSAM in Snort?

    <p>Sending messages to routers' access lists</p> Signup and view all the answers

    What is the purpose of the 'react' response rule option?

    <p>To block access to the session if the rule is triggered</p> Signup and view all the answers

    What is the function of the 'replace' rule option in Snort Inline?

    <p>To change the content of the packet to allow the packet to be sent without affecting the content in an adverse way</p> Signup and view all the answers

    What is the function of SnortSAM?

    <p>To provide an IPS like action for snort</p> Signup and view all the answers

    What is the function of the 'sdrop' action in Snort Inline?

    <p>To drop the packet without generating an alert</p> Signup and view all the answers

    What is the purpose of the 'flexresp' plugin?

    <p>To send reset packets to the sender or recipient</p> Signup and view all the answers

    What is the difference between the 'drop' and 'sdrop' actions in Snort Inline?

    <p>The 'drop' action generates an alert while the 'sdrop' action does not</p> Signup and view all the answers

    What is a limitation of SnortSAM?

    <p>It is not widely used</p> Signup and view all the answers

    What is the purpose of the 'rst_snd' keyword in the 'flexresp' plugin?

    <p>To send a reset packet to the sender</p> Signup and view all the answers

    What is the purpose of Snort Inline?

    <p>To add new functionality to snort</p> Signup and view all the answers

    What is the requirement to enable flex response?

    <p>Compile snort from source</p> Signup and view all the answers

    What is the primary function of Session Interception in an IPS?

    <p>Terminating TCP connections by sending a reset packet</p> Signup and view all the answers

    What is the risk associated with altering access lists in Snort?

    <p>Self-inflicted Denial of Service</p> Signup and view all the answers

    What is the purpose of the flexresp plugin in Snort?

    <p>To allow Snort to act as a session interception IPS</p> Signup and view all the answers

    What can happen when Snort detects an attack and ends the TCP connection using RST?

    <p>Session Interception IPS identification</p> Signup and view all the answers

    What is the primary function of SnortSAM in Snort?

    <p>To send messages to routers access lists to prevent hostile traffic</p> Signup and view all the answers

    What can happen during the lag between the detect and the attack when SnortSAM is used?

    <p>Exploit beating the attempted block</p> Signup and view all the answers

    What is the purpose of the 'resp' rule option?

    <p>To send a reset packet to the sender or recipient</p> Signup and view all the answers

    Which of the following plugins require changes to the Snort configuration?

    <p>Flex response, Snort Inline, and SnortSAM</p> Signup and view all the answers

    What is the purpose of the 'react' rule option?

    <p>To send a message back to the browser or to send a warning to the client browser</p> Signup and view all the answers

    What is the purpose of the 'replace' rule option in Snort Inline?

    <p>To change the content of the packet to allow it to be sent without affecting the content</p> Signup and view all the answers

    What is the purpose of SnortSAM?

    <p>To provide an IPS like action for Snort</p> Signup and view all the answers

    What is the difference between the 'drop' and 'sdrop' actions in Snort Inline?

    <p>The 'drop' action generates an alert, while the 'sdrop' action does not</p> Signup and view all the answers

    What is required to enable flex response?

    <p>Building Snort from source with the flexresp plugin</p> Signup and view all the answers

    What is the limitation of using SnortSAM?

    <p>It requires running another program on top of Snort</p> Signup and view all the answers

    What is the purpose of the 'proxy' keyword in the react option?

    <p>To indicate the proxy port if the system runs on a proxy</p> Signup and view all the answers

    What is the requirement for using the react option?

    <p>Using the react option only with TCP protocol rules</p> Signup and view all the answers

    What is the purpose of the react rule option in Snort?

    <p>To block the TCP session</p> Signup and view all the answers

    What happens when the content of a TCP packet matches the 'verybadthings' pattern in the Snort rule?

    <p>The packet is blocked and the session is terminated</p> Signup and view all the answers

    What is required to test the Snort rule with the react option?

    <p>A TCP transmission with a message that contains 'verybadthings'</p> Signup and view all the answers

    What is the purpose of the modified checkrule.py script?

    <p>To add a message to TCP packets</p> Signup and view all the answers

    What is the purpose of the sid field in the Snort rule?

    <p>To identify the rule in the Snort database</p> Signup and view all the answers

    What is the result of adding the rule to the local.rules file?

    <p>The rule is applied to the TCP packets in real-time</p> Signup and view all the answers

    What is a false positive indicator?

    <p>When a rule generates an unexpected alert or more alerts than expected</p> Signup and view all the answers

    Why might you need to tune your IDS?

    <p>To alert and log more information than needed</p> Signup and view all the answers

    What is a potential cause of a false negative?

    <p>All of the above</p> Signup and view all the answers

    What is the purpose of the flow preprocessor?

    <p>To monitor port scans</p> Signup and view all the answers

    What should you do when verifying a rule that generates an unexpected alert?

    <p>Verify the rule and any equipment that is part of the rule</p> Signup and view all the answers

    What is the purpose of uncommenting the decoder configurations?

    <p>To tailor decoders and preprocessors</p> Signup and view all the answers

    What should you do with rule sets that are not needed?

    <p>Comment them out</p> Signup and view all the answers

    What is the problem with using pass rules?

    <p>They can make it difficult to detect attacks</p> Signup and view all the answers

    What is the purpose of the http_inspector preprocessor?

    <p>To troubleshoot and find false positives</p> Signup and view all the answers

    What is the advantage of suppression rules over thresholding rules?

    <p>Suppression rules are more flexible</p> Signup and view all the answers

    What should you do with individual rules in a rule set that do not cover operations in your system?

    <p>Comment them out</p> Signup and view all the answers

    What is the purpose of setting the reassemble to 'noalerts'?

    <p>To prevent false positives</p> Signup and view all the answers

    What is the term for when a rule generates an unexpected alert or more alerts than expected?

    <p>False Positive</p> Signup and view all the answers

    Why is it necessary to tune your IDS?

    <p>To reduce the number of false positives</p> Signup and view all the answers

    What is the primary function of the flow preprocessor?

    <p>To detect port scans</p> Signup and view all the answers

    What can be disabled if monitoring portscans is not important to your system?

    <p>Flow preprocessor</p> Signup and view all the answers

    What is a potential cause of a false negative?

    <p>All of the above</p> Signup and view all the answers

    What is the purpose of uncommenting decoder configurations?

    <p>To tailor decoders and preprocessors</p> Signup and view all the answers

    What is the purpose of tailoring decoders and preprocessors in Snort?

    <p>To reduce false positives</p> Signup and view all the answers

    Why should you disable the flow-portscan preprocessor if not tracking portscans?

    <p>To prevent unnecessary alerts</p> Signup and view all the answers

    What is the problem with using pass rules in Snort?

    <p>They make it nearly impossible to detect attacks</p> Signup and view all the answers

    What is the advantage of suppression rules over thresholding rules?

    <p>They are more flexible</p> Signup and view all the answers

    Why should you comment out individual rules in a rule set that do not cover operations in your system?

    <p>To reduce false positives</p> Signup and view all the answers

    What is the purpose of setting the reassemble to 'noalerts' in Snort?

    <p>To disable alerts for non-security related issues</p> Signup and view all the answers

    What should you do when performing tuning?

    <p>Use the no_alerts option to remove unnecessary data</p> Signup and view all the answers

    What is the purpose of tailoring the rule set?

    <p>To uncomment/comment out rules that are needed or not needed in your Snort configuration</p> Signup and view all the answers

    Why should you avoid using pass rules?

    <p>Because they are not specific enough to handle exceptions to rules</p> Signup and view all the answers

    What should you consider when tuning individual rules?

    <p>Making rules as specific as possible</p> Signup and view all the answers

    What is the purpose of tuning individual rules?

    <p>To avoid false positives</p> Signup and view all the answers

    Why should decoder configurations be commented out when developing rules?

    <p>To verify that rules are still sending alerts</p> Signup and view all the answers

    What should you do with rules that are not specific enough?

    <p>Use thresholding to limit the number of alerts produced</p> Signup and view all the answers

    What is the purpose of the flow preprocessor?

    <p>To provide service to the flow-portscan preprocessor</p> Signup and view all the answers

    When can the frag 3 preprocessor be disabled?

    <p>If your snort sensor is behind a firewall or router that does fragment reassembly</p> Signup and view all the answers

    What information does the http_inspector preprocessor provide?

    <p>Value information that can generate a lot of data</p> Signup and view all the answers

    What is the benefit of making a backup of your snort.conf file?

    <p>To ensure that changes can be reversed if needed</p> Signup and view all the answers

    Why should changes to the snort.conf file be made one at a time?

    <p>To test the configuration before making additional changes</p> Signup and view all the answers

    What is the purpose of commenting out the decoder configurations?

    <p>To disable alerts on certain rules</p> Signup and view all the answers

    When can the frag 3 preprocessor be disabled?

    <p>When a firewall or router does fragment reassembly</p> Signup and view all the answers

    What is the purpose of the flow preprocessor?

    <p>To provide service to the flow-portscan preprocessor</p> Signup and view all the answers

    What happens when the decoder configurations are uncommented?

    <p>Alerts on certain rules are disabled</p> Signup and view all the answers

    What information does the http_inspector preprocessor provide?

    <p>Value information that can generate a lot of data</p> Signup and view all the answers

    Why is it recommended to make changes to the snort.conf file one at a time?

    <p>To test the configuration before making additional changes</p> Signup and view all the answers

    What is the purpose of using the no_alerts option when performing tuning?

    <p>To remove noise data that provides no benefit</p> Signup and view all the answers

    What should you do with rules that are not common services run on a network?

    <p>Comment them out</p> Signup and view all the answers

    What is the purpose of pass rules?

    <p>To remove false positives</p> Signup and view all the answers

    What is a recommended approach when a rule cannot be specific enough?

    <p>Using thresholding</p> Signup and view all the answers

    Why is it recommended to avoid using pass rules?

    <p>Because they should be replaced by thresholding</p> Signup and view all the answers

    What is the purpose of tuning individual rules?

    <p>To make rules more specific to avoid false positives</p> Signup and view all the answers

    Study Notes

    Snort Tuning and Thresholding

    • False Positives: Unexpected alerts or more alerts than expected, requiring rule verification to ensure it's not a real intrusion attempt. • False Negatives: Undetected intrusions, caused by traffic encryption, network configuration problems, day zero attacks, faulty signatures, poor change management, and Snort sensor administration problems.

    Initial Configuration and Tuning

    • Decoders and Preprocessors: + Uncomment decoder configurations + Disable unnecessary preprocessors (e.g., flow, frag, stream) based on system requirements + Set reassemble to "noalerts" for stream preprocessor • Tailoring Decoders and Preprocessors: + http_inspector preprocessor: set with no_alerts when not used for troubleshooting + flow-portscan preprocessor: disable if not tracking portscans • Tailoring the Rule Set: + Comment out unnecessary rule sets and individual rules + Restrict rule sets to only use web technology and database used in the system

    Thresholding and Suppression

    • Threshold Rules: + Limit: alert only the first X number of events + Threshold: alert every X times + Both: alert only the X number of thresholds • Global Thresholds: use sig_id set to 0, meaning all rules • Suppression Rules: similar to threshold rules, can suppress by signature, source or destination address, or CIDR network block

    Using Snort as an IPS

    • React Rule Option: used to block TCP sessions, e.g., blocking TCP packets containing "verybadthings"

    Snort Limitations and Considerations

    • Open Source: may have limited documentation and require troubleshooting • Configuration: only the first step, requiring manual user intervention and a plan to stop intrusions • NIDS: one layer in network security, should be used in conjunction with other layers (IPS, Firewall, VPN) • Initial Configuration: essential to success, consider systems, topography, and network environment • Sensor Placement: prioritize systems to watch, use natural bottlenecks, and enable port mirroring or use a hub

    Deploying Snort

    • Important Key Points: + Snort is not a plug-and-watch solution + Understand what protections Snort provides and how it affects network and defense systems + Snort can't check encrypted traffic, but can check SSL Proxies • Securing the Sensor: harden the sensor, disable unnecessary services, apply patches and updates, and utilize robust authentication • Connecting Sensors: connect Snort to a database to save alerts and tie them to a sensor### Snort Rules

    • Snort rules are used to detect and alert on various types of network traffic
    • There are different types of rule sets available, including:
      • Exploit rules: detect known exploits
      • Finger rules: detect known types of finger attacks
      • FTP rules: detect known file transfer protocol attacks
      • ICMP-info rules: detect ICMP issues (not enabled by default)
      • IMAP rules: detect attacks against IMAP email services
      • Info rules: detect normal traffic on a healthy, secure network (not enabled by default)
      • Local rules: holds all custom rules created
      • Misc rules: holds rules that are not included in other categories
      • Multimedia rules: detect multimedia that is against company policy (not enabled by default)
      • MySQL rules: detect attacks against MySQL servers
      • Netbios rules: detect attacks against Windows systems using the NetBIOS protocol
      • NNTP rules: detect attacks against the Network Time Protocol
      • Oracle rules: detect attacks against Oracle database servers
      • Other-IDS rules: detect traffic from other IDS services
      • P2P rules: detect traffic sent from peer-to-peer services (disabled by default)
      • Policy rules: detect traffic sent from security policy violating services (disabled by default)
      • Pop2 rules: detect attacks against POP2 email services
      • Pop3 rules: detect attacks against POP3 email services
      • Porn rules: detect a variety of off-color packets (disabled by default)
      • RPC rules: detect attacks against remote procedure call (RPC) services
      • Rservices rules: detect attacks against remote services (rsh, rlogin, rexec)
      • Scan rules: detect attacks against a variety of network and service scans
      • Shellcode rules: detect shell code in packet payloads (disabled by default)
      • SMTP rules: detect attacks against SMTP mail services
      • SQL rules: detect attacks against MSSQL Database servers
      • Telnet rules: detect attacks against telnet services
      • TFTP rules: detect attacks against TFTP Services
      • Virus rules: detect viruses (disabled by default, not used or maintained)
      • Web-attack rules: detect web attacks (disabled by default, not used or maintained)
      • Web-cgi rules: detect attacks against Common Gateway Interface (CGI) services
      • Web-client rules: detect attacks against mainly Microsoft Outlook services
      • Web-coldfusion rules: detect attacks against ColdFusion web application services
      • Web-frontpage rules: detect attacks against Microsoft FrontPage web authoring services
      • Web-iis rules: detect attacks against Microsoft Internet Information Server (IIS) web services
      • Web-misc rules: detect attacks against common web attacks
      • Web-php rules: detect attacks against webservers running PHP application services
      • X11 rules: detect attacks against remote X-Windows services

    Creating Your Own Rules

    • To create your own rule, you need to add it to any of the existing rules packs
    • The syntax for creating a rule includes:
      • "sid" option: the rule ID
      • "msg" option: a unique message describing what the rule has detected
    • Rule actions:
      • Alert: alerts and logs the packet when triggered
      • Log: only logs the packet when triggered
      • Pass: ignores or drops the packet
      • Activate: alerts and then activates a dynamic rule/rules
      • Dynamic: ignores until started by an activate rule, then acts as a log rule
    • Rule protocols:
      • TCP
      • UDP
      • IP
      • ICMP
      • Possible protocols in the future: ARP, IGRP, GRE, OSPF, RIP

    Testing Your Rule

    • To test your rule, you need to:
      • Configure your VM with a NAT network setup
      • Start Snort on your VM using the following command: sudo snort -A console -c snort.conf
      • Open another terminal window and send a ping call to test the rule
      • Verify that the rule worked by checking the console in the other window

    Snort Rule Syntax

    • Every rule requires at a minimum the "sid" option
    • It is also good practice to include a unique message describing what the rule has detected, "msg" option
    • When a rule is positive, the message is logged

    TCP Rules

    • TCP rules can alert or log connection-oriented communications between a source and destination
    • You can check the flag that is being sent with the packet
    • You do not need to check the flag, but you will alert/log every transaction between the source and host if you do not specify the flag

    UDP Rules

    • UDP rules can alert or log connectionless communications between a source and destination
    • You can specify the content of the packet to filter out false positives

    Non-Filtering Rule Options

    • Revision: used to mark the version of the rule
    • Nocase: removes case sensitivity for uricontent and content options
    • Session: allows the TCP session information to be captured
    • Stateless: changes when the alert is made, watching a TCP session and sending an alert once the session is completed### Flex Response
    • Flex Response is a plugin that allows Snort to act as a session interception IPS
    • Requires building Snort from source with the flexresp plugin
    • Allows Snort to send a reset packet to the sender, recipient, or both parties
    • Keywords: rst_snd, rst_rcv, rst_all, icmp_net, icmp_host, icmp_port, icmp_all

    React Response

    • The React response option is useful when blocking attacks that use the TCP session
    • Does not require compiling Snort from source
    • Only works on TCP protocol rules
    • Keywords: block, warn, msg, proxy

    Snort Inline and SnortSAM

    • Snort Inline adds new functionality to Snort, including two new actions and a new rule option
    • The two new actions are drop and sdrop, which allow Snort to drop offending packets
    • The new rule option is replace, which allows Snort to change the content of a packet
    • SnortSAM is a program that runs alongside Snort to provide IPS-like actions
    • SnortSAM requires patching Snort to provide a different output module

    Intrusion Prevention Strategies

    • Host-based memory and process protection
    • Session Interception
    • Gateway intrusion detection
    • Intrusion Prevention Risks: Session interception IPS identification, Exploit beating the attempted block, Self-inflicted Denial of service

    Tuning Snort

    • Tailor the decoder and preprocessors
    • Use the no_alerts option to remove unnecessary data
    • Tune individual rules to be as specific as possible
    • Use thresholding to limit the number of alerts produced by a single rule
    • Pass rules are used to remove false positives, but should not be used in favor of thresholding

    Decoder Configurations

    • There are six decoder configurations in the snort.conf file
    • These configurations disable alerts on certain rules
    • Should be commented out when developing rules and verified when active
    • Located under step 2 of the snort.conf file

    Preprocessors

    • Flow preprocessor provides service to the flow-portscan preprocessor
    • Frag 3 preprocessor is used for fragment reassembly
    • Http_inspector preprocessor provides valuable information, but can generate a lot of noise

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    Learn how to effectively deploy Snort as a Network Intrusion Detection System (NIDS) and configure the snort.conf file to ensure optimal performance. Understand the essential components required for successful Snort deployment. Quiz yourself on Snort setup and configuration.

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