I have a small LAMP Stack that hosts about 30 websites. Recently we had a number of sites become compromised with the eval(decode... garbage on large number of files. We cleaned that up and all the sites are working properly. We had a new attack where files were actually uploaded to the Wordpress sites with huge encoded files that contained the x64\x65\x28\x22\x22\x2C\x24\x69\x66\x65\x67\x29\x29\x29\x29\... and those files were accompanied by encrypted files called "ps". I scoured every site individually and cleaned up all the stray files/code (I even replaced some sites) then I used Wordfence to verify every site is clean. Even after all this I can still see outbound traffic in my tcpdumps that make be believe the server is still attacking wp-login.php due to the random URLs I see to those pages.
At this point I'm at a loss as to how to find where this malicious activity is originating on my server. There is no GUI on this machine, anybody have any ideas how I can track down the culprit?