I just mentioned that one user starts a process which is called "httpd".
31712 ftp_johndoe 20 0 35988 8828 1460 S 14.0 0.0 1h50:31 httpd
28616 ftp_johndoe 20 0 5304M 43936 35080 S 4.0 0.2 0:02.72 /usr/bin/php5-cgi -c /var/www/vhosts/system/johndoe.net/etc/php.ini
31711 ftp_johndoe 20 0 35808 8608 1460 S 1.0 0.0 1h51:15 httpd
Well, I wondered why the process is called "httpd", because on debian apache starts no processes called "httpd".
If I lsof it I'm getting the following results:
httpd 28868 ftp_johndoe txt REG 253,0 10456 12335127 /usr/bin/perl
httpd 28868 ftp_johndoe mem REG 253,0 22952 12335108 /usr/lib/perl/5.14.2/auto/File/Glob/Glob.so
httpd 28868 ftp_johndoe mem REG 253,0 109888 12335102 /usr/lib/perl/5.14.2/auto/POSIX/POSIX.so
httpd 28868 ftp_johndoe mem REG 253,0 18672 12335109 /usr/lib/perl/5.14.2/auto/Fcntl/Fcntl.so
httpd 28868 ftp_johndoe mem REG 253,0 39256 12980353 /usr/lib/perl5/auto/Socket/Socket.so
httpd 31712 ftp_johndoe 63u IPv4 520937935 0t0 TCP server.name.com:38504->64.233.165.26:smtp (ESTABLISHED)
httpd 31712 ftp_johndoe 67u IPv4 520937969 0t0 TCP server.name.com:38536->64.233.165.26:smtp (ESTABLISHED)
httpd 31712 ftp_johndoe 73u IPv4 520937951 0t0 TCP server.name.com:38520->64.233.165.26:smtp (ESTABLISHED)
So I guess this is malware. But how can I find the script that starts the httpd process?