The File Transfer Protocol (FTP) has attracted renewed interest lately, but not in a good way: The bad guys are now using the 70s disco-era file transfer technology to serve up bot malware, and even as a backdoor into some enterprises that neglect to lock down their FTP servers.
Researchers at F-Secure have spotted a new wave of exploits that use FTP -- rather than a malicious URL, or the conspicuous email attachment -- to deliver their malware payloads. As SMTP and HTTP are much better filtered for malware, FTP might be the best transport protocol for a virus writer, says Mikko Hypponen, chief research officer for F-Secure. We've just started to observe this phenomenon -- it's not widespread yet, but likely to increase.
Last month, researchers at Finjan stumbled onto a cache of stolen FTP server administrative credentials that put nearly 9,000 FTP servers at some major global companies at risk, demonstrating just how widespread the old-school FTP remains at many organizations. Cybercriminals were selling a new crimeware package that would automatically infect those servers, some of which were from the world's top 100 domains. (See Stolen FTP Credentials Offered for Sale: Major Firms at Risk.)
F-Secures team last week discovered malicious Hallmark greeting card spam messages aimed at recruiting bots. The messages links to view the greeting instead take the victims to a bot-infected machine serving as an FTP site. The code it downloads is actually a variant of the Zapchast mIRC-bot, according to F-Secure. Instead of receiving the greeting, the user becomes a bot.
So why this retro-borne attack, especially when use of FTP is on the wane? FTP today is often a forgotten or unknown hole in the security of an organization -- not many enterprises bother to monitor it. And for bot herders, its just another means of moving malware.
FTP is more popular than anyone knows -- a lot of people still send FTP stuff back and forth because its easy to do, says Taher Elgamal, CTO of Tumbleweed Communications, which sells secure FTP software. And from the bad guys perspective, FTP is less likely to be blocked than an instant message, he says. FTP is sort of left alone because its supposed to be an old thing no one cares about. But its an effective protocol for transferring large files... Thats why were seeing this [attack] phenomenon.
Elgamal says the bad guys can hop on Port 80 and ship FTP through that port, for example, and a firewall wouldnt block the file transfer. Some Internet gateways scan for FTP traffic, such as F-Secures Internet Gatekeeper, which does so by default. But many organizations just dont bother scanning for FTP traffic at all either because they dont consider it a risk or they dont realize its being used, security experts say.
Still, the FTP-borne attack obviously wont ever be as big as an HTTP-borne one. Most companies wouldn't set up a new FTP site any more -- it's so old school. [But] the [FTP] sites that are out there are old and often forgotten about and poorly protected, F-Secures Hypponen says.
Have a comment on this story? Please click "Discuss" below. If you'd like to contact Dark Reading's editors directly, send us a message.
Kelly Jackson Higgins is the Executive Editor of Dark Reading. She is an award-winning veteran technology and business journalist with more than two decades of experience in reporting and editing for various publications, including Network Computing, Secure Enterprise ... View Full Bio