Researchers at Zscaler warned that the attackers behind the 'CookieBomb' attack are still hard at work compromising users through legitimate websites.
"First, there is the obfuscation of a small JS inclusion into a potentially legitimate site," explained Zscaler researcher Chris Mannon, in a blog post. "This is where the CookieBomb sets a name, special variable, expiry date, and access path for the eventual infection. If the cookie is not readily available, it will create one for you and redirect you to another obfuscated hidden iFrame. Once the hidden site is visited, it will read the cookie's expiry date and provide redirection and infection at a later point to avoid security vendor detection."
At least 54 legitimate websites have been infected so far with malicious code, Michael Sutton, vice president of security research at Zscaler, told SecurityWeek. Though Zscaler has not official tally of infected victims, any visitors to the compromised sites could be impacted, he said, adding that researchers at the Malware Must Die blog first wrote about the attack July 17.
The most notable site among them is splashtop.com, though the malicious content has since been removed, Mannon noted.
"The curious thing about this situation is that few AV vendors have taken note of the good research. The final dropped file is being detected by only 7/45 vendors," Mannon blogged.
According to Sutton, no zero-day vulnerabilities are implemented in the attack.
"CookieBomb is similar to most of the attacks that we see in that attackers are not targeting specific sites but rather writing automated scripts and injecting content into as many legitimate sites as possible to impact visitors to those cites," Sutton said. "CookieBomb is particularly active at the moment and a trait of this particular attack, which isn't always employed, involves the use of browser cookies to track previous infections for a potential victim."