Linux Security and File Systems
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Questions and Answers

What option of mount.cifs specifies the user that appears as the local owner of the files of a mounted CIFS share when the server does not provide ownership information?

  • username
  • uid (correct)
  • owner
  • gid

Where should private keys be created and stored?

  • On a system with a secure connection
  • On a shared network drive
  • On a public key server
  • On a system where they will be used (correct)

What is the primary purpose of NSEC3 in DNSSEC?

  • To authenticate a DNS server
  • To provide information about DNSSEC key signing keys
  • To prevent zone enumeration (correct)
  • To sign a DNS zone

Which command is used to change the SELinux context for a user?

<p>newrole (B)</p> Signup and view all the answers

What is a key used for encryption that is different from the key used for decryption?

<p>An asymmetric key (D)</p> Signup and view all the answers

Which file is used to configure AIDE?

<p>/etc/aide/aide.conf (B)</p> Signup and view all the answers

Which of the following is an example of a behavioral-based HID technique?

<p>Anomaly-based detection (C)</p> Signup and view all the answers

Which command is used to set an extended attribute on a file in Linux?

<p>setfattr (A)</p> Signup and view all the answers

What is the purpose of ndpmon?

<p>To monitor the network for neighbor discovery messages from new IPv6 hosts and routers (D)</p> Signup and view all the answers

Which option in an Apache HTTPD configuration file enables OCSP stapling?

<p>httpd-ssl.conf (B)</p> Signup and view all the answers

What is an asymmetric key used for?

<p>Encryption and decryption using different keys (C)</p> Signup and view all the answers

Why should private keys have a sufficient length for the algorithm used for key generation?

<p>To prevent brute-force attacks (B)</p> Signup and view all the answers

Which of the following database names can be used within a Name Service Switch (NSS) configuration file?

<p>group, shadow, passwd (B)</p> Signup and view all the answers

Which parameter to openssl s_client specifies the host name to use for TLS Server Name Indication?

<p>-servername (B)</p> Signup and view all the answers

Which of the following lines in an OpenSSL configuration adds an X509v3 Subject Alternative Name extension for the host names example.org and www.example.org to a certificate?

<p>subjectAltName = DNS: <a href="http://www.example.org">www.example.org</a>, DNS:example.org (B)</p> Signup and view all the answers

What is a buffer overflow?

<p>A type of software vulnerability (B)</p> Signup and view all the answers

Which tool can be used to manage the Linux Audit system?

<p>auditd (C)</p> Signup and view all the answers

What is the difference between a SetUID and SetGID bit?

<p>SetUID allows a file to be executed with the permissions of the file owner, while SetGID allows a file to be executed with the permissions of the group owner (C)</p> Signup and view all the answers

Which of the following sections are allowed within the Kerberos configuration file krb5.conf?

<p>[realms] (A), [plugins] (D)</p> Signup and view all the answers

What is the purpose of the Linux Audit system?

<p>To detect intrusions and system changes (A)</p> Signup and view all the answers

What is Linux Malware Detect?

<p>A tool to detect malware on a Linux system (B)</p> Signup and view all the answers

What is a Trojan?

<p>A type of malware that disguises itself as legitimate software (B)</p> Signup and view all the answers

What is a rogue access point?

<p>An unauthorized access point that is set up to look like a legitimate one (B)</p> Signup and view all the answers

Which command is used to generate DNSSEC keys?

<p>dnssec-keygen (A)</p> Signup and view all the answers

What is the purpose of file ownership in Linux systems?

<p>To restrict access to files only to their owner (A)</p> Signup and view all the answers

What is a DoS attack?

<p>An attack that floods a network or server with traffic to make it unavailable (D)</p> Signup and view all the answers

What is a trust anchor?

<p>A root certificate that is trusted by a particular CA (C)</p> Signup and view all the answers

What is the purpose of getfacl?

<p>To view the access control list of a file (B)</p> Signup and view all the answers

What is a man-in-the-middle attack?

<p>An attack that intercepts communications between two parties to steal information (A)</p> Signup and view all the answers

Which of the following commands adds a new user to FreeIPA?

<p>ipa user-add usera --first User --last A (B)</p> Signup and view all the answers

What is the purpose of rkhunter?

<p>To detect rootkits and other security threats (C)</p> Signup and view all the answers

What is a certificate chain?

<p>A sequence of certificates used to verify the authenticity of a digital certificate (B)</p> Signup and view all the answers

Which of the following commands changes the source IP address to 192.0.2.11 for all IPv4 packets which go through the network interface eth0?

<p>iptables -t nat -A POSTROUTING -o eth0 -j SNAT --to-source 192.0.2.11 (B)</p> Signup and view all the answers

What is the purpose of a Certificate Authority (CA)?

<p>To issue and sign X.509 certificates (A)</p> Signup and view all the answers

Which directive is used in an OpenVPN server configuration to send network configuration information to the client?

<p>push (D)</p> Signup and view all the answers

Which of the following DNS records are used in DNSSEC?

<p>RRSIG (B)</p> Signup and view all the answers

Which command is used to add users using SSSD’s local service?

<p>sss_useradd (C)</p> Signup and view all the answers

What is the primary purpose of a mechanism that allows a server to provide proof of its own identity to clients?

<p>To verify the identity of the server to clients (D)</p> Signup and view all the answers

Which command is used to install and configure a new FreeIPA server?

<p>ipa-server-install (C)</p> Signup and view all the answers

What is the purpose of a certificate signing request (CSR) in cryptography?

<p>To request a digital certificate from a CA (B)</p> Signup and view all the answers

What is the primary goal of cryptography?

<p>To send secret messages (B)</p> Signup and view all the answers

What type of activity does HID primarily monitor for?

<p>Unauthorized access attempts (C)</p> Signup and view all the answers

What is the benefit of using HID?

<p>Real-time detection of security incidents (C)</p> Signup and view all the answers

What is a ciphertext?

<p>The encrypted message (A)</p> Signup and view all the answers

What is the purpose of the auditctl command?

<p>To define an audit rule (A)</p> Signup and view all the answers

What is a rootkit?

<p>A type of malware that disguises itself as legitimate software (D)</p> Signup and view all the answers

What is the purpose of the ebtables command?

<p>To display ebtable rules (A)</p> Signup and view all the answers

What does the ulimit command control in a Linux system?

<p>The maximum number of open file descriptors (A), The maximum number of user processes (B), The maximum size of written files (C)</p> Signup and view all the answers

What is the purpose of the SSLStrictSNIVHostCheck configuration option in Apache HTTPD?

<p>To serve the virtual host only to clients that support SNI (D)</p> Signup and view all the answers

What is the purpose of the SSLRequestClientCert directive in Apache HTTPD?

<p>To request a client certificate but not require it (C)</p> Signup and view all the answers

What is true about a Root CA certificate?

<p>It is a self-signed certificate (B)</p> Signup and view all the answers

What is the best practice for implementing HID?

<p>Configure HID to alert security personnel of potential security incidents (C)</p> Signup and view all the answers

How are SELinux permissions related to standard Linux permissions?

<p>SELinux permissions are verified after standard Linux permissions (A), Standard Linux permissions override SELinux permissions (B)</p> Signup and view all the answers

What command is used to set the owner and group of a file in Linux?

<p>chown (C)</p> Signup and view all the answers

What is the purpose of an access control list in Linux?

<p>To specify fine-grained permissions for users and groups (A)</p> Signup and view all the answers

What is the purpose of the OCSP stapling mechanism?

<p>To provide proof of the revocation status of its own SSL/TLS certificate (C)</p> Signup and view all the answers

What is the purpose of the openvas-nvt-sync command?

<p>To update NVTs from the OpenVAS NVT feed (B)</p> Signup and view all the answers

What is the purpose of a DNSKEY record in DNSSEC?

<p>To sign a DNS zone (C)</p> Signup and view all the answers

What is the purpose of AIDE?

<p>To detect intrusions and system changes (A)</p> Signup and view all the answers

What is phishing?

<p>A type of social engineering attack (D)</p> Signup and view all the answers

What is an X.509 Certificate?

<p>A digital document that verifies the identity of a website (D)</p> Signup and view all the answers

Which DNS record is used to map an IP address to a hostname?

<p>PTR (D)</p> Signup and view all the answers

What is the purpose of DNS over TLS and DNS over HTTPS?

<p>To provide secure communication between DNS clients and servers (D)</p> Signup and view all the answers

What is the purpose of a Certificate Revocation List (CRL)?

<p>A list of X.509 certificates that have been revoked by a particular CA (A)</p> Signup and view all the answers

Which of the following statements is true about chroot environments?

<p>The chroot path needs to contain all data required by the programs running in the chroot environment (A)</p> Signup and view all the answers

What is social engineering?

<p>A type of attack that exploits human psychology to gain access to sensitive information (D)</p> Signup and view all the answers

Which of the following information, within a DNSSEC-signed zone, is signed by the key signing key?

<p>The zone signing key of the zone (D)</p> Signup and view all the answers

What happens when you run the command cryptsetup luksOpen /dev/sda1 crypt-vol?

<p>It maps the LUKS device to the name 'crypt-vol'. (A)</p> Signup and view all the answers

What is true about eCryptfs?

<p>eCryptfs cannot be used to encrypt only directories that are the home directory of a regular Linux user. (A)</p> Signup and view all the answers

How does TSIG authenticate name servers?

<p>Using a secret key shared between the servers. (D)</p> Signup and view all the answers

Which components are part of FreeIPA?

<p>Kerberos KDC, Directory Server, and Public Key Infrastructure (B)</p> Signup and view all the answers

Which utility is used to generate keys for DNSSEC?

<p>dnssec-keygen (A)</p> Signup and view all the answers

What is the purpose of the pam_cracklib PAM module?

<p>To check new passwords against dictionary words and enforce complexity (D)</p> Signup and view all the answers

What makes the contents of the eCryptfs encrypted directory ~/Private available to the user?

<p>ecryptfs-mount-private (A)</p> Signup and view all the answers

What is the purpose of IP sets in Linux?

<p>To group together IP addresses referenced by netfilter rules (B)</p> Signup and view all the answers

Which of the following is an example of a HID tool?

<p>Security information and event management (SIEM) system (A)</p> Signup and view all the answers

What does the X509 certificate contain?

<p>Basic Constraints with CA:TRUE, pathlen:0 (B)</p> Signup and view all the answers

What is the purpose of an extended attribute in Linux?

<p>To store additional metadata about a file (A)</p> Signup and view all the answers

Which command is used to configure rkhunter?

<p>./etc/rkhunter.conf (C)</p> Signup and view all the answers

What is true about AppArmor and SELinux?

<p>AppArmor is less complex and easier to configure than SELinux. (D)</p> Signup and view all the answers

Which command disables the automatic password expiry for the user usera?

<p>chage --maxdays -1 usera (B)</p> Signup and view all the answers

What is the purpose of the iptables command?

<p>To accept all TCP traffic on port 20 and 21 for the IP address 10.142.232.1 (B)</p> Signup and view all the answers

Which access control model is established by using SELinux?

<p>Mandatory Access Control (MAC) (A)</p> Signup and view all the answers

Which option of the openvpn command should be used to ensure that ephemeral keys are not written to the swap space?

<p>--mlock (D)</p> Signup and view all the answers

Which of the following namespaces are used in Linux Extended File Attributes?

<p>trusted, user, system (D)</p> Signup and view all the answers

What is the purpose of TSIG in DNS?

<p>To sign DNS messages for secure communication (A)</p> Signup and view all the answers

What is the purpose of privilege escalation?

<p>An attack that exploits a vulnerability to gain elevated privileges (A)</p> Signup and view all the answers

Study Notes

Mounting and Access Control

  • The uid option in mount.cifs specifies the user that appears as the local owner of files on a mounted CIFS share when the server does not provide ownership information.
  • The setfacl command is used to set access control lists (ACLs) on files.

Security and Encryption

  • Private keys should be created on the systems where they will be used and should never leave them.
  • Private keys should have a sufficient length for the algorithm used for key generation.
  • A buffer overflow is a type of software vulnerability.
  • A symmetric key is a key used for encryption and decryption that is the same.
  • An asymmetric key is a key used for encryption that is different from the key used for decryption.

DNS and DNSSEC

  • NSEC3 is used to prevent zone enumeration in DNSSEC.
  • TSIG is used to sign DNS messages for secure communication.
  • DNSSEC validation is performed on behalf of clients by a recursive name server.

System Security and Auditing

  • The Linux Audit system is used to detect intrusions and system changes.
  • ausearch is a command used to search and filter the audit log.
  • setfattr is a command used to set extended attributes on files.
  • getfattr is a command used to get extended attributes of files.

Network Security

  • A honeypot is a network security tool designed to lure attackers into a trap.
  • An IP set is a group of IP addresses and networks that can be referenced by netfilter rules.
  • A man-in-the-middle attack is an attack that intercepts communications between two parties to steal information.

Certificates and Authentication

  • A trust anchor is a root certificate that is trusted by a particular Certificate Authority (CA).
  • A certificate chain is a sequence of certificates used to verify the authenticity of a digital certificate.
  • OpenVPN uses ephemeral keys that are not written to the swap space.

Access Control and Security

  • Mandatory Access Control (MAC) is established by using SELinux.
  • The chattr command is used to set extended attributes on files.
  • The getfacl command is used to view the access control list of a file.### Linux Security and Administration
  • SELinux permissions are verified after standard Linux permissions
  • The chown command is used to set the owner and group of a file in Linux
  • Wireshark capture filters include port range 10000:tcp-15000:tcp and tcp portrange 10000-15000
  • The openvas-nvt-sync command is used to update NVTs from the OpenVAS NVT feed
  • The execute permission bit allows a file to be executed

Automated Scans

  • Host scans can be automated on a Linux system using cron
  • OpenSCAP is not used to automate host scans

Access Control

  • An access control list in Linux specifies fine-grained permissions for users and groups
  • The purpose of an access control list is to specify permissions for users and groups

NFS Authentication

  • Kerberos authentication was added to NFS in version 4

OCSP Stapling

  • OCSP stapling is a mechanism that allows a server to provide proof of the revocation status of its own SSL/TLS certificate

FreeIPA Server

  • The ipa-server-install command installs and configures a new FreeIPA server, including all sub-components, and creates a new FreeIPA domain

OpenSSL

  • The openssl req command is used to generate a certificate signing request (CSR) using an existing private key

Cryptography

  • Cryptography is the art of sending secret messages
  • A ciphertext is the encrypted message
  • A plaintext is the original message before encryption

HID (Host-based Intrusion Detection)

  • HID monitors for unauthorized access attempts
  • HID tools include security information and event management (SIEM) systems

Rootkits

  • A rootkit is a type of malware that disguises itself as legitimate software
  • chkrootkit is a tool used to check for rootkits on a Linux system

ebtables

  • The ebtables command is used to display all ebtable rules contained in the table filter, including their packet and byte counters

Snort-stat

  • snort-stat reads syslog files containing Snort information and generates port scan statistics

LUKS Devices

  • cryptsetup luksDelKey is used to delete a key from a LUKS device
  • cryptsetup luksOpen is used to open a LUKS device

eCryptfs

  • eCryptfs is a stacked cryptographic filesystem for Linux
  • eCryptfs does not store the contents of all files in an archive file similar to a tar file with an additional index to improve performance

Password Expiry

  • chage is used to change the password expiry information for a user
  • chage --maxdays none disables password expiry for a user

TSIG

  • TSIG authenticates name servers in order to perform secured zone transfers using a secret key that is shared between the servers

FreeIPA Components

  • FreeIPA components include Kerberos KDC, Directory Server, and Public Key Infrastructure
  • DHCP Server is not a component of FreeIPA

DNSSEC

  • dnssec-keygen is used to generate keys for DNSSEC
  • DNSSEC is used to provide authentication and integrity of DNS data
  • TSIG authenticates name servers in order to perform secured zone transfers using a shared secret key

X.509 Certificates

  • An X.509 certificate contains information about the identity of a website
  • A Certificate Revocation List (CRL) is a list of X.509 certificates that have been revoked by a particular CA

HID Tools

  • HID tools include security information and event management (SIEM) systems
  • Antivirus software is not a type of HID tool

AppArmor and SELinux

  • AppArmor and SELinux are both Linux security modules
  • SELinux is a Linux kernel module, whereas AppArmor is implemented in user space only
  • SELinux stores information in extended file attributes, whereas AppArmor does not maintain file-specific information and states

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Quiz about Linux security and file systems, including mounting CIFS shares and private key management.

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