A sophisticated hacking scheme seen early last year is affecting an increasing number of web servers, including one owned by a major online advertising company, Finjan Software has said.
It appears that a single gang is behind the attacks, since the malicious software it spreads is storing login and password details on one server in Spain, said Yuval Ben-Itzhak. Finjan is trying to get the ISP to shut it down, he said.
A web server of an online advertising company that serves 14 million banner ads to other websites has also been hacked, Ben-Itzhak said. That means that the PC of anyone who visits a legitimate site hosting a malicious banner ad could potentially be infected if their computer isn't patched, he said.
"You can imagine the magnitude," Ben-Itzhak said.
Ben-Itzhak declined to identify the company, but said Finjan contacted it last week about the problem. At least 10,000 other websites were serving up malicious code in December, although Finjan stopped counting, Ben-Itzhak said.
The latest problems show that the power of this particular hacking gang appears to be growing since it was identified early last year. At that time, Finjan said it found a number of web servers that had been hacked in order to serve malicious code to visitors. The attackers used several methods to hide their tracks and infect a maximum number of PCs.
Further, hackers also record the IP addresses of crawlers used by search engines and reputation services, which evaluate the risk in visiting certain websites. Those page requests are then served with legitimate content.
The code looks for at least 13 software vulnerabilities in order to place a Trojan horse program on the PC.
The hackers also regularly change the vulnerabilities that the attack looks for in order to increase the chances a computer can become infected, Ben-Itzhak said. After the PC is infected, the malware can start collecting data on the machine, such as documents and passwords. Finjan has dubbed the attack "random js Trojan."
Finjan asserts that anti-virus software isn't as effective since the attack code can change so frequently. The company has a browser plug-in, called SecureBrowsing, that analyses the content of a Web page as it's being served, looking for traces of malicious code and then warning users. It also sells an enterprise-level appliance with scanning technology.
Finjan isn't the only company with that kind of technology. Exploit Prevention Labs, which was recently acquired by security company AVG, also has a product called LinkScanner that analyses Web page content for malware, and McAfee has a service called SiteAdvisor that ranks the health of a website. All three companies offer free versions of their products.