Crimeware grifters scamming naive phishers

Phishing exploitation kits can be picked up for free on the internet but these packages are regularly backdoored, according to a new study.

Security researchers at the University of California, Santa Barbara, have confirmed that inexperienced phishers are in effect doing the legwork for more wily grifters. Many phishing kits distributed in the digital underground hand over data collected to coders. "These phishing kits target two classes of victims: the gullible users from whom they extort valuable information and the unexperienced phishers who deploy them," the researchers (Marco Cova, Christopher Kruegel, and Giovanni Vigna) conclude.

Phishing kits typically bundle all the content required to replicate a targeted web site, including HTML pages, JavaScript and CSS files, and media files, such as Flash clips.

By cleaning up and analysing data from the PhishTank database the researchers found that 61 of 150 unique phishing kits running live contained backdoors. Of 353 working phishing kits obtained on the digital underground, 129 (or more than a third) contained hidden backdoors. "We consider a kit to be backdoored if it sends the phished information to addresses other than those found in clear in the kit's code," the researchers explain.

The vast majority of phishing kits email compromised information to a user selected email address (the drop site). Less than one per cent of the sample analysed by Santa Barbara team either posted the information on a compromised server or sent it to a third party location.

Any site set up with a compromised phishing kit would surreptitiously send harvested data to a third party (often via a webmail address). Sometimes this might happen after a cybercrook takes an expensive web malware exploitation kit, adds a backdoor, and starts to distribute compromised copies for free, notes security consultant and blogger Dancho Danchev. He added that more sophisticated crooks go one step further in attempting to use software bugs in exploit kits, such as Zeus and Pinch, to seize control of botnets.

All in all the adage of no honour among thieves seems to apply just as well to the underground digital economy as old-fashioned blaggers.

The use of backdoors by phishers and the compromise of exploit tools have been covered by security watchers in the past, but the University of California study is one of the first to look systematically into the issues. The research, There is No Free Phish: An Analysis of “Free” and Live Phishing Kits, was presented at a Usenix workshop of offensive technologies in San Jose late last month. ®