2. SElinux (Security Enhanced Linux)SELinux is an implementation of a flexible mandatory access control architecture in the Linux operating system. The SELinux architecture provides general support for the enforcement of many kinds of mandatory access control policies, including those based on the concepts of Type Enforcement(R), Role- Based Access Control and Multi-Level Security.
SELinux is basically App permission tool which controls which activities a system allows each user, process, and daemon, with very precise specifications. However, it is mostly used to confine daemons like database engines or web servers that have more clearly-defined data access and activity rights. This limits potential harm from a confined daemon that becomes compromised. Ordinary user-processes often run in the unconfined domain, not restricted by SELinux but still restricted by the classic Linux access rights.
3. IPtablesWith the enhanced features available with the IPtables you can implement a greater level of security for your Linux machine.
IPtables can maintain and inspect the tables of IP packet filter rules in the Linux kernel. Several different tables may be defined. Each table contains a number of built-in chains and may also contain user-defined chains. Each chain is a list of rules which can match a set of packets. Each rule specifies what to do with a packet that matches.
4. PAM (Pluggable Authentication Modules)Linux-PAM is a system of libraries that handle the authentication tasks of applications (services) on the system. The principal feature of the PAM approach is that the nature of the authentication is dynamically configurable. In other words, the system administrator is free to choose how individual service-providing applications will authenticate users.
Linux-PAM separates the tasks of authentication into four independent management groups: account management; authentication management; password management; and session management.
account – provide account verification types of service: has the user’s password expired?; is this user permitted access to the requested service?
authentication – authenticate a user and set up user credentials. Typically this is via some challenge-response request that the user must satisfy: if you are who you claim to be please enter your password.
password – this group’s responsibility is the task of updating authentication mechanisms. Typically, such services are strongly coupled to those of the auth group. Some authentication mechanisms lend themselves well to being updated with such a function. Standard UN*X password-based access is the obvious example: please enter a replacement password.
session – this group of tasks cover things that should be done prior to a service being given and after it is withdrawn. Such tasks include the maintenance of audit trails and the mounting of the user’s home directory. The session management group is important as it provides both an opening and closing hook for modules to affect the services available to a user.
5. AuditThe 2.6 Linux kernel is a log keeper in Linux. It logs events such as system calls and file access. These logs can then be reviewed by the user to determine possible security breaches such as failed login attempts or a user failing to access system files. This functionality, called the Linux Auditing System.
auditd is also responsible for writing audit records to the disk. You can easily check out vulnerabilities using the ausearch or aureport utilities. Configuring the audit rules is also done with the auditctl utility.