Thursday, April 25, 2013

Could the AP Twitter hack have been prevented?

Twitter hacks can cause a lot of damage. It is news of this week that the Associated Press Twitter account got compromised, and sent a tweet announcing that the White House had been hit by a terrorist attack, and that President Obama was injured. The dynamics of the hack are not clear yet, even though some sources claim that the AP people might have been victim of a spearphishing attack.

What is sure is that the hack had a huge, unprecedented effect on the stock market. Right after the malicious tweet was sent, the New York stock exchange suddenly fell more than 150 points. The market recovered short afterwards (after it was clear that the announcement was a hoax), but somebody could definitely have made a lot of money from this event.

This is the first time that people realize that Tweets can have a large effect on financial institutions. The question that people are asking is: could this compromise have been avoided? The answer is maybe. At the last NDSS Symposium we presented a paper titled "COMPA: Detecting Compromised Accounts on Social Networks." The goal of the paper is to detect, and block, messages that are sent by compromised social network accounts, just like the AP one. Our system leverages a simple observation: people develop habits when using social networks. These habits include connecting to the network at specific times, using certain applications / clients to interact with the network, including links to specific domain in their messages, and so on. When an account gets compromised, the malicious messages that are sent are likely to show differences from this behavior. We developed a system, called COMPA, that learns the typical behavior of users on social networks, and raises an anomaly if a user sends a message that does not comply with the learned behavior.

We ran COMPA on the offending Tweet sent by the AP account. More precisely, we learned the historical behavior of the account, and we checked the malicious tweet against it. COMPA detected the tweet as anomalous. In particular, the tweet was sent from the web, while the AP operators typically use the SocialFlow app. In addition, the tweet does not include a URL, which is something that pretty much every news tweet contains. This is not a surprise to us. When the Fox News Politics account got hacked in 2011, COMPA was able to detect the offending tweet as anomalous too.

We think that the type of behavioral modelling that we ran in COMPA is the way in which social networks should implement their detection of compromised accounts algorithms, and we hope to see this type of techniques deployed in the wild in a near future.

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