Known as Gumblar by ScanSafe and Troj/JSRedir-R by Sophos and Gumblar (as known as cybersha),[1] this botnet first appeared in 2009. It is characterized by redirecting user's Google searches and installing rogue security software.
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Visitors to an infected site will be redirected to an alternative site containing further Malware, which was once gumblar.cn, but has now switched to a variety of domains. The site sends the visitor an infected PDF that is opened by the visitor's browser or Acrobat Reader. The PDF will then exploit a known vulnerability in Acrobat to gain access to the user's computer. On the new variations of Gumblar, it is redirecting users to sites running the fake anti virus.
The virus will find FTP clients such as FileZilla and Dreamweaver and download the clients' stored passwords. It also enabled promiscuous mode on the network card, allowing it to sniff local network traffic for FTP details. It is one of the first viruses to incorporate an automated network sniffer.
Using passwords obtained from site admins, the host site will access a website via FTP and infect the website. It will download large portions of the website and inject malicious code into the website's files before uploading the files back onto the server. The code is inserted into any file that contains a <body> tag, such as HTML, PHP, JavaScript, ASP and ASPx files. The inserted PHP code contains base64-encoded JavaScript that will infect computers that execute the code. In addition, some pages may have inline frames inserted into them. Typically, iframe code contains hidden links to certain malicious websites.
The virus will also modify .htaccess and HOSTS files, and create images.php files in directories named 'images'. The infection is not a server-wide exploit. It will only infect sites on the server that it has passwords to.
Different companies use different names for gumblar and variants. Initially, the malware was connecting to gumblar.cn domain but this server was shutdown later. However, many badware variants have emerged after that and they connect to various malicious servers via iframe code.
Gumblar resurfaced in January 2010, stealing FTP usernames and passwords and infecting HTML, PHP and Javascript files on webservers to help spread itself.[2] This time using multiple domains to make it harder to detect/stop.[3]
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