"It reroutes a [victim's] traffic without them being aware ... It's so effective because it's quick to modify itself so antivirus can't detect it. It's great for a quick-hit attack," says Noa Bar-Yosef, senior security strategist with Imperva, which issued a security alert today on this attack technique that its researchers have spotted in the wild.
BITB is basically a "dumbed-down" MITB in which the attacker infects a user with its Trojan, either via a drive-by download or by luring the user to click on an infected link on a site. The Trojan reconfigures the victim's "hosts" file and reroutes the victim's traffic for a specific website -- say, a bank or an online retailer -- and to the attacker's own server posing as that site. Then the BITB attacker can intercept or modify the transaction. "It's difficult to detect," Bar-Yosef says, because the victim sees the same URL he or she was requesting.
Bar-Yosef says the BITB is a low-cost and relatively easy attack to wage. Nine Latin American banks have been targeted with this attack, and another attack went after Google for ad fraud. In the Google attack, the attackers basically reconfigured the search engine address of different Google regional URLs, such as www.google.co.uk, which was rerouted to the attacker's URL that appeared similar to the Google page. When the victim searches on the "Google" site, the request is sent to the attacker's server, thus letting the attacker collect ad clicks or steal the victim's persistent cookies, for instance.
That particular BITM attack was uncharacteristically simple to detect because the page wasn't a perfect match to the legitimate Google site, Bar-Yosef says, but in most cases, there are no obvious clues with these attacks.
Imperva's advisory on the attacks is here.
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