Firewall and Service Management on Linux Essay Example | Topics and Well Written Essays - 1000 words

Firewall and Service Management on Linux - Essay Example If the system is connecting to other systems for the purpose of sending data out, for any number of possible reasons, including data theft, or participation in a botnet as an example. netstat - an option lists all listening ports of TCP and UDP connections. It might be useful sometimes to be able to list them all when analyzing a client’s system, given that it gives the big picture. However, when context is needed, some more filtering should be done to get a better idea of the issues one is dealing with. Thus other commands need to be used in order to provide better context. However, if a port is open that the client system is not using then the port needs to be closed to protect the client system from an attacker. netstat –at shows all TCP (Transmission Control Protocol) port connections only. TCP statistics can show when a client system is being attacked, such as during denial of service attacks. TCP parameters which show dropped connection requests increase rapidly when under attack. netstat –ant shows the output without running a DNS query, which would slow down the command response time. Instead, it will only show the IP address without showing domain names. This might be more useful when time is of essence, and one needs answers fast in case of an attack on a client system. netstat –nlpu shows the process that owns listening UDP socket connections. sudo netstat –nlpu shows the process owner and process ID (PID). This is useful in determining which program is running a process. This can help determine whether it is a rogue process or not, and can help in hardening client systems. The netstat command shows detailed statistics of each network connection, interface, routing tables, network protocols and it also displays other network-specific information. The netstat command helps us to deal with network issues in Linux.  Network administrators are also encouraged to have enhanced performance measurement when they use the netstat command.