My brush with the Gumblar worm

Some of you might have heard of the new worm out there known as the Gumblar worm or the gumblar.cn worm. It is a worm which has been spreading rampantly across the internet. This worm has become the scourge of the internet after the conficker worm. The Gumblar worm has two ugly sides to it, both of which I have been exposed to.

This was way back in March, when we were performing a company's website assessment. The company had outsourced their website development activity to a organization that designs websites. The company had run into a few security issues including Directory traversal vulnerabilities and weak passwords which the web design company had caused. Once the website was up, I opened up the page to see my Avast Anti-virus light up like a Christmas tree, with a malware alert for a "JS:Redirect" worm. Needless to say upon exploring the source in the php and html files, I found that a large piece of javascript code, which had no apparent business being on the page, was there. It was obfuscated code, which obviously caused the worm to propogate. The Javascript code for Gumblar is given below:

I have removed the Gumblar worm code as some AV apps were throwing up alerts from their content filtering engines. Please check elsewhere for a copy of the code.

The gumblar worm infects the PC when the PC opens up the website which is infected the malicious javascript.












The execution of the malicious code results in a backdoor being installed which attaches itself to Internet Explorer and also manipulates Google searches. Furthermore the worm is also known to disable anti-virus software, install fake av applications and also sends out spam. This is the one facet of the Gumblar worm. The other facet of the Gumblar worm, is worse and is extremely worrisome for a security professional. Gumblar also steals FTP credentials and appends itself to pages hosted in the webserver, thereby wreaking havoc to a webserver. This means to say that Hosting providers and webservers hosted by organizations may well have already been seriously compromised. FTP credentials have been stolen several webpages hosted in webservers all ovetr the world have been affected by the gumblar worm. The number of attacks over the last week have grown by 188% and counting and has accounted for over 42% of the malware detected all over the world. The number of infected websites has jumped from 800 to over 3000 in a matter of a few weeks.

As you can see, the gumblar botnet really goes two different types of systems. One it goes after PCs, where the PC is infected and the Google searches, Internet Explorer and the vulnerabilities in Adobe Acrobat are exploited. The other system is the Webserver, where it goes after FTP passwords and then appends the code onto all the web pages in the webserver. I first experienced this worm in March of this year and the worm has now started surfacing in all its glory. So, for all of you, here are some tips to stay safe and keep your website safe:
1. Latest AV Definitions: The biggest issue has been that Antivirus vendors except, I think, Avast and Kaspersky have not woken up to this issue till recently. Please make sure that your AV definitions are up and functional against Gumblar's many variants.
2. FTP Credentials: This is a good time to run a thorough manual and automated scan of the webserver and change the FTP credentials for all users in the system. It would also make sense for organizations hosting their web content with hosting providers to talk to them and see how their dealing with the situation. Also, please make sure that the FTP passwords are stored securely and that there is adequate encryption or hashing which is used to protect the same.
3. NoScript: For ordinary users out there, please use NoScript with Mozilla Firefox, it goes the distance in protecting you from the malicious javascript in websites against executing and infecting your PC.
4. Hosting and Web Design organizations: Please make sure that your hosting providers also take the same precautionary measures. In case you are having your website being designed by others, please make sure you test it in a staging environment before deploying it over the Internet. You might be aiding in the propogation of the worm.
5. IPS signatures: I already know for a fact that ISS Proventia has signatures released for the Gumblar worm. I am sure others would have also done so. Please keep the IPS updated for the Gumblar sigs.