Finger Bomb

Finger Bomb
Some finger daemons allow redirecting the finger to remote sites. To finger
through several sites, an intruder could use:
finger username@hostA@hostB
The finger will go through hostB then to hostA. This helps hackers cover their
tracks because hostA will see a finger coming from hostB instead of the
original service. This technique has been used to go through firewalls themselves if
they are not properly configured. This can happen by using the command
finger user@host@firewall
A denial of service attack may happen when an intruder types:
finger username@@@@@@@@@@@@@@@@@@@@@hostA
The repeated @ causes the finger to recursively finger the same machine
repeatedly till the memory and hard drive swap space fill up. This causes the machine
to crash or slow to an unusable speed.
Risk: Medium
Fix: Disable fingerd by commenting out the finger line in inetd.conf and kill -HUP
inetd process. Some finger daemons such as GNU finger allow you to turn off
redirection.
Patch:
GNU Finger