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Part IV: Hacking Operating Systems
Figure 12-8:
Using Amap
to check
application
versions.
✓ netstat shows the services running on a local machine. Enter this
command while logged in:
netstat –anp
✓ List Open Files (lsof) displays processes that are listening and files
that are open on the system.
To run lsof, log in and enter this command at a Linux command
prompt: lsof –i +M. The lsof command can come in handy when
you suspect that malware has found its way onto the system.
Countermeasures against attacks
on unneeded services
You can and should disable the unneeded services on your Linux systems.
This is one of the best ways to keep your Linux system secure. Like reducing
the number of entry points (such as open doors and windows) in your house,
the more entry points you eliminate, the fewer places an intruder can break in.
Disabling unneeded services
The best method of disabling unneeded services depends on how the
daemon is loaded in the first place. You have several places to disable services,
depending on the version of Linux you’re running.
If you don’t need to run a particular service, take the safe route: Turn it off!
Just give people on the network ample warning that it’s going to happen in the
event someone needs the service for their work.
inetd.conf (or xinetd.conf)
If it makes good business sense — that is, if you don’t need them — disable
unneeded services by commenting out the loading of daemons you don’t use.
Follow these steps: