Friendly spam: account hijacking and unintended consequences


In the past week, this blogger received links from two friends hawking shady pharmaceutical products: one was sent from a GMail account, and the other directly scrawled on the Facebook wall. This was odd, to say the least. Both friends remain gainfully employed, and unlikely to dabble in direct marketing on the sides: one is at MSFT, and the other works in financial services in Manhattan. Instead they had become victims of an account takeover, perhaps falling for a phishing scam, maybe logging into their accounts from a public computer infected by malware, or perhaps in the worst case scenario one of their personal machines had been 0wned.

So far, nothing new: in modern society, phishing attacks and large-scale machine compromise, compliments of Adobe, Sun/Oracle and MSFT are par for the course. What is unusual is the way the attackers are trying to leverage access: sending spam to other email address on the contact list. All things considered, this is a very mild outcome. A couple of factors may be at work:

  • Spam is economically viable. So much that attackers do not bother with trying to extract more value from compromised accounts. The revenue opportunity in spam has been well-studied in the security literature. The novel twist here is that the message is coming from a friend, and may have even higher click-through rates. (Keeping in mind that spamming is a very noisy activity. Eventually one of the friends on that contact list is bound to reply and inform the victim that their account has been 0wned.)
  • There is a surplus of compromised accounts out there, so much that attackers do not have the time to manually sort through each one and identify interesting ones. Presumably the personal email account of a financial analyst is worth more than that of an average Hotmail user. Even though it is not their work email, there may still be connections, interesting messages or stepping stones to other accounts. Using that account for indiscriminate spam seems inefficient, a waste of opportunity.
  • Attackers have not been able to automate the classification of each account as high/low value target. If so this is only a temporary roadblock. Given the profile information from an account (very likely includes the real name) it would be relatively easy for an individual to run a Google search for that person. Facebook accounts makes this easier by identifying networks/groups/past employers. Even running simple keyword searches in mail eg for names of banks, phrases appearing in legal briefings, could be used as the basis of heuristics to locate accounts with useful information.

Finally the proliferation of spam from friendly channels could be an encouraging sign that spam filters have gotten very good– to the point that attackers find it necessary to take over legitimate accounts and exploit existing trust relationships to their contacts as more reliable delivery mechanism. In that case the war on spam would have the highly ironic side-effect of increasing the pressure on existing user accounts.

CP

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