Fraudsters are experimenting with a new type of phishing kit capable of restricting certain users from ever reaching exploit pages – just the latest tactic to keep researchers of their scent and their ruses alive longer.
Limor Kessem, an intelligence expert at RSA's FraudAction Research Lab, said this week in a blog post that the "bouncer" kit allows attackers to employ the same sense of exclusivity enforced at popular nightclubs through VIP lists.
But this isn't a club you want to get into.
“If your name is not on the list, you're staying out,” Kessem wrote. “The bouncer phishing kit targets a preset email list for each campaign. A user ID value is generated for the targeted recipients, sending them a unique URL for access to the attack.”
Those not on the email list – particularly, researchers who might impede the operation – are redirected to a page with the “404 page not found” error message. For those unlucky enough to be on the list, the phishing kit is coded to copy specific files to a temporary folder, and to redirect victims to another page designed to prompt the user to enter login credentials.
"[T]raditional phishers like to cast as wide of a net as possible, but with this tactic the phisher is laser-focusing the campaign in an effort to collect only the most pertinent credentials for his purposes," Kessem wrote. "Keeping out uninvited guests also means avoiding security companies and prompt take-downs of such attacks."
RSA found that each phishing kit targeted an average of 3,000 users, which included a mix of webmail users and corporate email addresses, including those of bank employees. The kits also exploit zero-day vulnerabilities in plug-ins used on blogging sites, like WordPress, in order to compromise and hijack users' web pages to distribute malware.
RSA researchers also believe that the phishing kits could be used “as part of spear phishing campaigns to gain a foothold for a looming advanced persistent threat (APT)-style attack.”