Sunday, April 18, 2010

Moral Hazard: URL shorteners must improve malware prevention

Suffice it to say that my job duties include trying to help reduce malicious URLs being transmitted over Windows Live Messenger.
As you can likely imagine, URL shorteners (TinyURL, Bit.ly, etc.) give me conniptions.
Blocking the root domain is not feasible as the majority of URL shortener use is not malicious.
Can you say "whack-a-mole"?
Bit.ly, as an example, claims to be scanning URLs for malware, but with 40 million plus shortened URLs a day, they are definitely missing their share of malware-lade URLs.
TinyURL suffers from the same challenges; even though they have a strict Terms of Use, endless malicious URLs are shortened via TinyURL who seems to only employ a reactive prevention model (report it and they'll remove it).
Thus, topping the list of URLs being passed via Messenger on any given day is often the likes of tinyurl.com/y6v689z.
Click and a Russian free web host offers you fotos16.com, a Trojan-Downloader.Win32.Banload variant.
What's old is new again (first detected in 2006), but no less effective when coupled with simple social engineering. Simply, the Banload Trojan downloads other Trojans and aims to steal your banking credentials.
The victim receives an IM, often from a trusted contact, that evokes Facebook content: "Hey, check out my latest Facebook pics!" No shocker there, someone targeting popular Internet resources as part of their attack methodology? Groundbreaking.
But you know what? It works over and over and over again.
All day long.
Until the cows come home.
So what does our shortened URL with a social networking lure get us?
All sorts of bonus goodies.
This sample helped remind me of how much I love NetworkMiner.
Thrash my trusty Windows XP VM, capture the network traffic, and voila, we quickly learn all we need to know.
Our Banload friend got busy in the 80 seconds I let it run in my home lab environment.
14 sessions, 23 DNS queries, 11 file downloads, and three authenticated (credentials captured as they are passed in the clear) SMTP exchanges with Brazilian free mail hosts.
Gotta have somewhere to send all those stolen credentials right?



Soapbox time.
I liken the failure of URL shortening providers to better protect users from malware to a moral hazard.
A moral hazard is "the lack of any incentive to guard against a risk when you are protected against it (as by insurance)."
A strongly worded Terms of Use does not indemnify the likes of Bit.ly, TinyURL, and others.
Too many people are getting pwnzored.
Better efforts to prevent malicious abuse of URL shortening services must ensue.

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