The "onload if this" website infection
Of course the title of this post is only part of the infection.
The typical type of infection I’m going to discuss first looks more like this:
The domain this iframe directs to and the long string of characters (kzjev…) before the closing iframe tag can be different, but from what I’ve seen, the rest is typically the same.
Other domains we’ve seen include, but are not limited to:
Using PowerGrep, we’ve been able to remove this infection quite quickly, however, just removing it doesn’t mean your website is safe – not by a long shot.
Upon further analysis, we found that these infections were remotely controlled, locally injected.
What I mean is that the control of the infection is handled remotely, however, the infection process itself is local to the files on the website.
First of all, in some of the sites that had these infections, we found the old gifimg.php file in the images folders. Some sites have various plugins and some of the plugins have their own images folder. The gifimg.php was in there as well so look through all folders for the gifimg.php file. As you may know from our previous post, this file allows the hackers to send commands to your website from where ever they are – this is remotely controlled part.
Keep in mind that not all of the websites where we found the “onload if this” infection had the gifimg.php file. Just because you don’t find that file doesn’t mean you don’t have the “onload if this” infection.
Before we get too focused on the “onload if this” type of infections, let me state that other infections were injected the exact same way.
Here again, we’ve seen various other URLs such as:
just to list a few.
The infectious code that generates this infection is:
Which deobfuscates to:
Which, as you can see, is one of the domains listed above. The original PHP script injects this malscript into various pages it finds throughout the site.
You can search for and delete this script (inside the script tags) all you want. If it comes back over and over again, then you might have the original php code, or something similar in one your files. It’s these repeat infections that are the worst because you could waste hours of time scanning through your files, looking at the code, removing everything you believe is malicious and then it comes right back again – over and over.
Typically for a repeat infection our advice would have been to scan your PC for viruses and trojans with a different anti-virus program than what you’ve been using. However, in this case, that might eliminate the original infection, but the repeat infections are the result of this php code.
Unfortunately, the only way you can detect this is to find it in the code on your website. We requested full FTP access from the clients who had this infection so we could look at all the files. No remote (meaning a scanner that scans from outside your website) can find this. The PHP code dynamically generates the webpage so you’ll never see the malicious remote control code in the source code of your browser.
How did these sites get infected originally?
By the same method used to infect thousands if not millions of sites – via stolen FTP login credentials. FTP login credentials are saved on a local computer and stealing them gives hackers a valid method for accessing the files on a website – valid login credentials.
I’m working up a full write-up on steps to take to prevent compromised FTP login credentials, but it’s not ready just yet.
If your website is getting hacked over and over again, you should scan all your website files for any occurrence of this string:
Don’t just delete any file with that string in it because we have seen various files where that is used legitimately, however, close examination of any file with that string is suggested.
If you need assistance in locating this code or deobfuscating code let me know and I’ll try to help you.
If you have any other domains or URLs to add to our lists above, please send them to me at firstname.lastname@example.org or post them as a comment here.