I have a server that keeps on being used to launch attacks on other people.
What the person/script is doing is using /tmp to possibly run a script to send out many many packets out.
Nocster then just shuts off my server and we co-operate with them to try to fix it. They have tried changing the permissions on /tmp, but then it seems like it happens again.
It has happened almost 6 times now, and they are starting to get angry!!
Look at doing the following (after you wipe the system, restore the os, and restore from a backup made prior to the hack):
* Disable telnet.
* Limit SSH access to specific IP addresses.
* Disable direct root login.
* Remove unnecessary packages / software.
* Harden the kernel against synflood and basic DOS attacks.
* Remove common user access to compilers and fetching software (wget, fetch, lynx, etc.).
* Ensure /tmp is in its own partition with noexec, nosuid.
* Ensure kernel and software is up to date.
* Remove unnecessary users and groups.
* Install chkrootkit, logwatch, tripwire.
* Install a firewall, and port scan detector.
* For Apache servers, install mod_security and configure for use with FrontPage, PHPMyAdmin, Site Studio, and other common applications.
* Secure DNS Servers
* Utilize firewall automation to mitigate brute force FTP, syn floods, mail bombs, and out-of-network trojan’d servers from impacting your servers
It is important to note that security is an ongoing venture. Even if you were to take all of the steps listed above, you would still have a regular routine of review, update, research, patch, etc.
I watched a server get hacked real time and they where downloading shell scripts and tarballs or DoS engines and more toys from a remote server and then execute the script and other toys as the user that the web server is running as 'nobody'.
I have found all sorts of backdoor scripts, eggdrops, bnc and other nasty stuff. One set of files I looked over was also infected with a virus that would infect all the 'ELF' binaries on the server.
After all of the files have been installed in /tmp a eggdrop bot will join a IRC channel and wait for commands on who to attack next or they are used for other illegal activities like helping distribute warez or stolen information.