CS3009 Cryptography and Network Security Week 13-14 PDF

CS3009 – Cryptography and Network Security Week 13-14 Network Security Network security is activity designed to protect the usability and integrity of network data It includes both hardware and software technologies Network security terms: Vulnerabilities: attack surface or fl...

CS3009 – Cryptography and Network Security Week 13-14 Network Security Network security is activity designed to protect the usability and integrity of network data It includes both hardware and software technologies Network security terms: Vulnerabilities: attack surface or flaw in the system that can be exploited by attacker Threats: condition/circumstance which can cause damage to the system/asset. It can be intentional or unintentional. Attacks: an intended action to cause damage to system/asset 2 Vulnerabilities Primary vulnerabilities in network Technology vulnerabilities – security weaknesses in technology Configuration vulnerabilities – incorrect network configurations Security policy vulnerabilities – lack of security policy imposement 3 Technology Vulnerabilities Computer and network technologies have inbuilt security vulnerabilities: TCP/IP protocol vulnerabilities (HTTP, FTP are inherently unsecure) Operating system vulnerabilities (Windows, Linux have security problems) Network equipment vulnerabilities (routers, switches have security weaknesses) 4 Configuration Vulnerabilities Network administrator need to correctly configure the computing and network devices to compensate: Unsecured user accounts (information transmitted insecurely across network) System account with easily guessed passwords Unsecured default settings within products Misconfigured internet services (untrusted sites on dynamic webpages) Misconfigured network equipment (misconfiguration itself cause security problem) 5 Security Policy Vulnerabilities The network can pose security risk if users do not follow the security policies. Lack of written security policy (policies in booklet) Politics (political battles makes it difficult to implement security policies) Lack of continuity (easily cracked or default password allows unauthorized access) Logical access control. Not applied (imperfect monitoring allows unauthorized access) Disaster recovery plan nonexistent (lack of disaster recovery plan allows panic when someone attacks the enterprise) 6 Threats The people eager, willing and qualified to take advantage of each security vulnerability, and they continually search for new exploits and weaknesses. Following classes of threats: Structured threats: implemented by a technically skilled person who is trying to gain access to your network Unstructured threats: created by an inexperienced/ non- technical person who is trying to gain access to your network External threats: occurs when someone from inside your network creates a security threat to your network Internal threats: occurs when someone from outside your network creates a security threat to your network 7 Common terms Hacker: hacker is a person intensely interested in requiring secret and recondite workings of any computer operating system. Hackers are most often programmers. Phreaker: A phreaker is an individual who manipulates the phone network to cause it to perform a function that is normally not allowed. A common goal of phreaking is breaking into the phone network. Spammer: An individual who sends large number of unsolicited e-mail messages. Spammers often use viruses to take control of home computers to use these computers to send out their bulk messages. Phisher: A phisher uses e-mail or other means in an attempt to trick others into providing sensitive information, such as credit card no or password etc. White hat: Individuals who use their abilities to find vulnerabilities in systems or networks and then report these vulnerabilities to the owners of the system so that they can be fixed. Black hat: Individuals who use their knowledge of computer to break into system that they are not authorized to use. 8 Attacks The threats use a variety of tools, scripts and programs to launch attack against network and network devices. Following are the classes of attacks: Reconnaissance: is a primary step of computer attack. It involve unauthorized discovery of targeted system to gather information about vulnerabilities. The hacker surveys a network and collects data for a future attacks Access: it is just what it sounds like: an attempt to access another user account or network device through improper means. Denial of Service (DoS): DoS attacks are often implemented by a hacker as a means of denying a service that is normally available to a user or organization. DoS attacks involve either crashing the system or slowing it down to the point that it is unusable. Worms, viruses and trojan horses: malicious code is the kind of harmful computer code designed to create system vulnerabilities leading to back doors and other potential damages to files and computing systems. It’s a type of threat that may not be blocked by antivirus software on its own.9 Access attack can consist of the following: 1. Password attack 2. Trust exploitation 3. Port redirection 4. Traffic Interception attack 5. Man-in-the-Middle attack 6. Social engineering 7. Phishing 10 Password attacks Password attacks can be implemented using brute-force attack (repeated attempts to identify users password) Methods for computing passwords: Dictionary cracking Brute-force computation 11 Trust exploitation Trust exploitation refers to an attack in which an individual takes advantage of a trust relationship within a network. 12 Port redirection A type of trust exploitation attack that uses a compromised host to pass traffic through a firewall that would otherwise be dropped. 13 Traffic Interception Attack In this attack, the cyber criminal uses software such as packet sniffers to monitor network traffic and capture passwords as they’re passed. Similar to eavesdropping or tapping a phone line, the software monitors and captures critical information. 14 Man-in-the Middle attack A man-in-the-Middle attack requires that the hacker have access to network packets that come across a network 15 Social engineering Social engineering is the art of manipulating people so they give up confidential information. Phishing—Emails, texts, etc. sent to fool users into providing their credentials, clicking a link that installs malicious software, or going to a fake website. Spear phishing—Similar to phishing but with better crafted, tailored emails/texts which rely on information already gathered about the users. For example, the hacker may know that the user has a particular type of insurance account and reference it in the email or use the company’s logo and layout to make the email seem more legitimate. Baiting—Attackers leave infected USBs or other devices in public or employer locations in the hopes they will be picked up and used by employees. Quid quo pro—The cyber criminal impersonates someone, like a helpdesk employee, and interacts with a user in a way that requires getting information from them. 16 Denial of service (DoS) DoS attacks are often implemented by a hacker as a means of denying a service that is normally available to a user or organization. DoS attacks involve either crashing the system or slowing it down to the point that it is unusable 17 Distributed DoS DDoS uses attack methods similar to standard DoS attack but operates on a much large scale 18 IPSecurity (IPSec) IPSecurity (IPSec) is a collection of protocols designed by the Internet Engineering Task Force (IETF) to provide security for a packet at the network level. Two Modes Two Security Protocols Security Association Virtual Private Network Internet Key Exchange (IKE) Figure TCP/IP protocol suite and IPSec Figure Transport mode and tunnel modes of IPSec protocol Note IPSec in the transport mode does not protect the IP header; it only protects the information coming from the transport layer. Figure Transport mode in action Figure Tunnel mode in action Note IPSec in tunnel mode protects the original IP header. Figure Encapsulating Security Payload (ESP) Protocol in transport mode Note ESP provides source authentication, data integrity, and privacy. Figure Authentication Header (AH) Protocol in transport mode Note The AH Protocol provides source authentication and data integrity, but not privacy. Table IPSec services Figure Simple inbound and outbound security associations Table Addresses for private networks Figure Private network Figure Hybrid network Figure Virtual private network Figure Addressing in a VPN Note IKE creates SAs for IPSec. E-mail architecture 5 0 Message Integrity An authenticated message 10 Compression A compressed message 11 Cryptographic Algorithms Note In e-mail security, the sender of the message needs to include the name or identifiers of the algorithms used in the message. Certificates It is obvious that some public-key algorithms must be used for e-mail security. 6 7 Position of PGP in the TCP/IP protocol suite 6 8 A scenario in which an e-mail message is authenticated and encrypted Confidentiality with One-Time Session Key A confidential message 13 Code Conversion Another service provided by PGP is code conversion. PGP uses Radix-64 conversion. Segmentation PGP allows segmentation of the message.  Key Revocation It may become necessary for an entity to revoke his or her public key from the ring. This may happen if the owner of the key feels that the key is compromised (stolen, for example) or just too old to be safe. PGP Packets Format of packet header Types of PGP Packet Literal data packet Compressed data packet Encrypted data packet Signature packet Session-key packet Public-key packet Public Key 30 Encrypted message Signed message Certificate message S/MIME Another security service designed for electronic mail is Secure/Multipurpose Internet Mail Extension (S/MIME). The protocol is an enhancement of the Multipurpose Internet Mail Extension (MIME) protocol. MIME 40 Radix-64 conversion  S/MIME S/MIME adds some new content types to include security services to the MIME. All of these new types include the parameter “application/pkcs7- mime,” in which “pkcs” defines “Public Key Cryptography Specification.” Cryptographic Message Syntax (CMS) To define how security services, such as confidentiality or integrity, can be added to MIME content types, S/MIME has defined Cryptographic Message Syntax (CMS). The syntax in each case defines the exact encoding scheme for each content type. Signed-data content type Enveloped-data content type Digest-data content type Authenticated-data content type SSL (Secure Socket Layer) transport layer security service originally developed by Netscape version 3 designed with public input subsequently became Internet standard known as TLS (Transport Layer Security) uses TCP to provide a reliable end-to-end service SSL has two layers of protocols SSL Architecture SSL Architecture SSL session an association between client & server created by the Handshake Protocol define a set of cryptographic parameters may be shared by multiple SSL connections SSL connection a transient, peer-to-peer, communications link associated with 1 SSL session SSL Record Protocol confidentiality using symmetric encryption with a shared secret key defined by Handshake Protocol IDEA, RC2-40, DES-40, DES, 3DES, Fortezza, RC4- 40, RC4-128 message is compressed before encryption message integrity using a MAC with shared secret key similar to HMAC but with different padding SSL Change Cipher Spec Protocol one of 3 SSL specific protocols which use the SSL Record protocol a single message causes pending state to become current hence updating the cipher suite in use SSL Alert Protocol conveys SSL-related alerts to peer entity severity warning or fatal specific alert unexpected message, bad record mac, decompression failure, handshake failure, illegal parameter close notify, no certificate, bad certificate, unsupported certificate, certificate revoked, certificate expired, certificate unknown compressed & encrypted like all SSL data SSL Handshake Protocol allows server & client to: authenticate each other to negotiate encryption & MAC algorithms to negotiate cryptographic keys to be used comprises a series of messages in phases Establish Security Capabilities Server Authentication and Key Exchange Client Authentication and Key Exchange Finish SSL Handshake Protocol Location of SSL and TLS in the Internet model 17.106  SSL ARCHITECTURE SSL is designed to provide security and compression services to data generated from the application layer. 1. Services 2. Key Exchange Algorithms 3. Encryption/Decryption Alogrithms 4. Hash Algorithms 5. Cipher Suite 6. Compression Algorithms 7. Crypography Parameter Generation 8. Session and Connections 17.10  Services Fragmentation Compression Message Integrity Confidentiality Framing Key Exchange Algorithms Key-exchange methods 17.109  NULL There is no key exchange in this method. No pre- master secret is established between the client and the server. Note Both client and server need to know the value of the pre-master secret. 17.11  RSA RSA key exchange; server public key 17.11  Anonymous Diffie-Hellman Anonymous Diffie-Hellman key exchange 17.11  Ephemeral Diffie-Hellman key exchange Ephemeral Diffie-Hellman key exchange 17.11 Fixed Diffie-Hellman Another solution is the fixed Diffie-Hellman method. All entities in a group can prepare fixed Diffie- Hellman parameters (g and p). Fortezza Fortezza is a registered trademark of the U.S. National Security Agency (NSA). It is a family of security protocols developed for the Defense Department. Encryption/Decryption Algorithms Encryption/decryption algorithms NULL The NULL category simply defines the lack of an encryption/decryption algorithm. Stream RC Two RC algorithms are defined in stream mode. Block RC One RC algorithm is defined in block mode. DES All DES algorithms are defined in block mode.  SELF STUDY: Differentiations between RC4, IDEA and Fortezza algorithms Hash Algorithm Hash algorithms for message integrity 17.118  Cipher Suite The combination of key exchange, hash, and encryption algorithms defines a cipher suite for each SSL session. 17.119  Compression Algorithms Compression is optional in SSLv3. No specific compression algorithm is defined for SSLv3. Therefore, the default compression method is NULL. Cryptographic Parameter Generation Calculation of master secret from pre-master secret Calculation of key material from master secret Extractions of cryptographic secrets from key material  Sessions and Connections Note In a session, one party has the role of a client and the other the role of a server; in a connection, both parties have equal roles, they are peers. A session and connections  Session State Session state parameters 17.12  Connection State Connection state parameters 17.12 Note The client and the server have six different cryptography secrets: three read secrets and three write secrets. The read secrets for the client are the same as the write secrets for the server and vice versa.  Four Protocols We have discussed the idea of SSL without showing how SSL accomplishes its tasks. SSL defines four protocols in two layers, 1. Handshake Protocol 2. ChangeCipher Spec Protocol 3. Alert Protocol 4. Record Protocol 17.12 Four SSL protocols 17.130 Handshake Protocol Handshake Protocol 17.131 Phase I of Handshake Protocol 17.132  Note After Phase I, the client and server know the following: ❏ The version of SSL ❏ The algorithms for key exchange, message authentication, and encryption ❏ The compression method ❏ The two random numbers for key generation 17.13 Phase II of Handshake Protocol 17.134  Note After Phase II, ❏ The server is authenticated to the client. ❏ The client knows the public key of the server if required. 17.13 Four cases in Phase II Phase III of Handshake Protocol 17.137  Note After Phase III, ❏ The client is authenticated for the server. ❏ Both the client and the server know the pre-master secret. 17.13 Four cases in Phase III Phase IV of Handshake Protocol Note After Phase IV, the client and server are ready to exchange data. Movement of parameters from pending state to active state Alert Protocol Alerts defined for SSL Record Protocol Processing done by the Record Protocol Calculation of MAC  SSL MESSAGE FORMATS As we have discussed, messages from three protocols and data from the application layer are encapsulated in the Record Protocol messages. 1. ChangeCipherSpec Protocol 2. Alert Protocol 3. Handshake Protocol 4. Application Data Record Protocol general header ChangeCipherSpec Protocol ChangeCipherSpec message Alert Protocol Alert message Handshake Protocol Generic header for Handshake Protocol Types of Handshake messages Virtual tributary types ClientHello message ServerHello message Certificate message ServerKeyExchange message CertificateRequest message ServerHelloDone message CertificateVerify message Hash calculation for CertificateVerify message ClientKeyExchange message Finished message Hash calculation for Finished message Application Data Record Protocol message for application data Transport Layer Security (TLS) The Transport Layer Security (TLS) protocol is the IETF standard version of the SSL protocol. The two are very similar, with slight differences.  Cipher Suite Another minor difference between SSL and TLS is the lack of support for the Fortezza method. TLS does not support Fortezza for key exchange or for encryption/decryption. Cipher Suite for TLS Master secret generation Key material generation  Alert Protocol TLS supports all of the alerts defined in SSL except for NoCertificate. TLS also adds some new ones to the list. Table 17.7 shows the full list of alerts supported by TLS. Handshake Protocol Hash for CertificateVerify message in TLS Hash for Finished message in TLS Record Protocol HMAC for TLS Introduction ⚫ Network Security ⚫ System Security − Protecting − User access ⚫ Network − Authentication equipment. controls ⚫ Network servers − Assignment of and transmissions. privilege ⚫ Eavesdropping. − Maintaining file and − Data Integrity file system integrity − Monitoring processes − Log-keeping − Backups Definitions ⚫ Intrusion − A set of actions aimed to compromise the security goals, namely ⚫ Integrity, confidentiality, or availability, of a computing and networking resource ⚫ Intrusion detection − The process of identifying and responding to intrusion activities ⚫ Intrusion prevention − Extension of ID with exercises of access control to protect computers from exploitation Intrusion Detection System ⚫ IDS - Definition − Monitors either a Network boundary (Network IDS) or a single host (Host IDS) in real-time, looking for patterns that indicate Attacks. ⚫ Functional Blocks.. − Sensor − Monitor − Resolver − Controller Contd... ⚫ Sensor ⚫ System Specific Data Gathering Component. ⚫ Track Network traffic, Log files, System behaviour ⚫ Monitor ⚫ Monitor Components, Get Events from Sensor. ⚫ Correlates Events against Behaviour-Model ⚫ Produce Alerts. ⚫ Resolver ⚫ Determine Response against Alerts. ⚫ E.g. Logging, Changing System Mechanism, Setting Firewall Rule etc. ⚫ Controller - Coordination and Administration Elements of Intrusion Detection ⚫ Primary assumptions: − System activities are observable − Normal and intrusive activities have distinct evidence ⚫ Components of intrusion detection systems: − From an algorithmic perspective: ⚫ Features - capture intrusion evidences ⚫ Models - piece evidences together − From a system architecture perspective: ⚫ Various components: audit data processor, knowledge base, decision engine, alarm generation and responses Components of Intrusion Detection System Audit Records system activities are observable Audit Data Preprocessor Activity Data Detection normal and intrusive Models Detection Engine activities have distinct evidence Alarms Action/Report Decision Decision Engine Table Intrusion Detection Approaches ⚫ Modeling − Features: evidences extracted from audit data − Analysis approach: piecing the evidences together ⚫ Misuse detection (a.k.a. signature-based) ⚫ Anomaly detection (a.k.a. statistical-based) ⚫ Deployment: Network-based or Host-based − Network based: monitor network traffic − Host based: monitor computer processes ⚫ Misuse Detection pattern matching Intrusion Patterns: intrusion Sequences of system calls, patterns of activities network traffic, etc. ⚫ Example: if (traffic contains “x90+de[^\r\n]{30}”) then “attack detected” Problems? Can’t detect new attacks Anomaly Detection probable intrusion activity measures ⚫ Define a profile describing “normal” behavior, then detects deviations. Any problem ? Relatively high false positive rates Anomalies can just be new normal activities. Anomalies caused by other element faults E.g., router failure or misconfiguration, P2P misconfig Host-Based IDSs ⚫ Use OS auditing and monitoring mechanisms to find applications taken over by attacker − Log all relevant system events (e.g., file/device accesses) − Monitor shell commands and system calls executed by user applications and system programs ⚫ Pay a price in performance if every system call is filtered ⚫ Problems: − User dependent: install/update IDS on all user machines! − If attacker takes over machine, can tamper with IDS binaries and modify audit logs − Only local view of the attack ⚫ Network IDSs ⚫ Deploying sensors at strategic locations − For example, Packet sniffing via tcpdump at routers ⚫ Inspecting network traffic − Watch for violations of protocols and unusual connection patterns − Look into the packet payload for malicious code ⚫ Limitations − Cannot execute the payload or do any code analysis ! − Even DPI gives limited application-level semantic information − Record and process huge amount of traffic − May be easily defeated by encryption, but can be mitigated with encryption only at the gateway/proxy − Comparison Host Based Network Based  Narrow in scope (watches only  Broad in scope (watches all specific host activities) network activities)  More complex setup  Easier setup  Better for detecting attacks from  Better for detecting attacks from the inside the outside  More expensive to implement  Less expensive to implement  Detection is based on what any  Detection is based on what can be single host can record recorded on the entire network  Does not see packet headers  Examines packet headers  Usually only responds after a  Near real-time response suspicious log entry has been made  OS-independent  OS-specific  Detects network attacks as payload  Detects local attacks before they hit is analyzed the network  Detects unsuccessful attack  Verifies success or failure of attacks attempts Hybrid Intrusion Detection  Are systems that combine both Host-based IDS, which monitors events occurring on the host system and Network-based IDS, which monitors network traffic, functionality on the same security platform.  A Hybrid IDS, can monitor system and application events and verify a file system’s integrity like a Host-based IDS, but only serves to analyze network traffic destined for the device itself.  A Hybrid IDS is often deployed on an organization’s most critical servers. Honeypots  Are decoy servers or systems setup to gather information regarding an attacker of intruder into networks or systems.  Appear to run vulnerable services and capture vital information as intruders attempt unauthorized access.  Provide you early warning about new attacks and exploitation trends which allow administrators to successfully configure a behavioral based profile and provide correct tuning of network sensors.  Can capture all keystrokes and any files that might have been used in the intrusion attempt. Passive System  Detects a potential security breach  Logs the information  Signals an alert on the console  Does not take any preventive measures to stop the attack Passive System Contd... Reactive/ Active System  Responds to the suspicious activity like a passive IDS by logging, alerting and recording, but offers the additional ability to take action against the offending traffic. Reactive/ Active System Contd... Architecture of Network IDS Signature matching (& protocol parsing when needed) Protocol identification TCP reassembly Packet capture libpcap Packet stream Signature Based IDS  Monitor network or server traffic and match bytes or packet sequences against a set of predetermined attack lists or signatures.  Should a particular intrusion or attack session match a signature configured on the IDS, the system alerts administrators or takes other pre-configured action.  Signatures are easy to develop and understand if you know what network behavior you’re trying to identify.  However, because they only detect known attacks, a signature must be created for every attack.  New vulnerabilities and exploits will not be detected until administrators develop new signatures.  Another drawback to signature-based IDS is that they are very large and it can be hard to keep up with the pace of fast moving network traffic. Anomaly Based IDS  Use network traffic baselines to determine a “normal” state for the network and compare current traffic to that baseline.  Use a type of statistical calculation to determine whether current traffic deviates from “normal” traffic, which is either learned and/or specified by administrators.  If network anomalies occur, the IDS alerts administrators.  A new attack for which a signature doesn’t exist can be detected if it falls out of the “normal” traffic patterns.  High false alarm rates created by inaccurate profiles of “normal” network operations. Issues False Negatives  When an IDS fails to detect an False Positives attack  Described as a false alarm.  False negatives occur when  When an IDS mistakenly the pattern of traffic is not reports certain “normal” identified in the signature network activity as malicious. database, such as new attack  Administrators have to fine patterns. tune the signatures or  False negatives are deceptive heuristics in order to prevent because you usually have no this type of problem. way of knowing if and when they occurred.  You are most likely to identify false negatives when an attack is successful and wasn’t detected by the IDS. Pros  Can detect external hackers, as well as, internal network-based attacks  Scales easily to provide protection for the entire network  Offers centralized management for correlation of distributed attacks  Provides defense in depth  Gives administrators the ability to quantify attacks  Provides an additional layer of protection Cons  Generates false positives and negatives  Reacts to attacks rather than preventing them  Requires full-time monitoring and highly skilled staff dedicated to interpreting the data  Requires a complex incident response process  Cannot monitor traffic at higher network traffic rates  Generates an enormous amount of data to be analyzed  Cannot deal with encrypted network traffic  It is expensive