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Attack Campaign Targets Facebook, Dropbox User Credentials

The goal of the attackers is not fully clear but the credential theft could set up sophisticated targeted attackers.

Researchers at security firm Cyphort have uncovered a five-year-old attack campaign that has quietly gone about the business of stealing user credentials for Dropbox, Facebook, and other applications unnoticed until now.

At this point, it does not appear the attackers are targeting specific organizations or industries, since their tentacles seem to have reached organizations ranging from energy companies to charities. According to Cyphort's McEnroe Navaraj, the intent of the data collection is unknown, but there is no shortage of ways for the credentials to be turned to the attackers' advantage.

The so-called NightHunter attack uses SMTP email for exfiltrating data rather than "more common CnC (command and control) mechanisms that use web protocols," Navaraj said in a blog post:

This could be to simply "hide (and steal data) in the plain sight" as organizations beef up web anomaly detection for dealing with advanced attacks.

It involves several different malware keyloggers, including Predator Pain, Limitless, and Spyrex. The unifying feature is that they all use SMTP (email) for data exfiltration. Email to social networking is like snail-mail is to email … it is outdated and often overlooked, so it can be a more stealthy way of data theft. So we called it NightHunter.

According to Cyphort, the company received a sample through a phishing email. The sample is a .net binary that steals users' credentials and sends them to a remote email server when executed. When researchers examined the sample, they also uncovered other similar samples in the wild as well. Navaraj said in the post:

These samples are delivered mostly through phishing emails. These emails are sent with DOC/ZIP/RAR attachments. You can get infected by opening a malicious document with scripting enabled. Most of the phishing emails are targeted towards personnel in finance/sales/HR departments. Sometimes actors may act as goods resale agents. We have seen cases where it was bundled with fake IDM/7zip installers. Most of these samples used keylogger tools to sniff data from the victim.

Cyphort co-founder Fengmin Gong notes that some of the servers used by the attackers are either private or have access protections that prevented the firm from looking into the upload account, so the actual number of infected machines is higher than the 1,800 compromised machines the company is aware of.

"This attack is ongoing and we continue to monitor it," Gong tells Dark Reading. "The attackers are very aggressive in their data-collection methodology, as well as the intervals of data exfiltration. Given the systematic nature of the actors behind this campaign, we are speculating that they are still in a 'reconnaissance stage' targeting credentials of high-level executives, but at this point it is impossible to speculate on their endgame with any degree of certainty."

Still, he says he believes the attackers may be using big-data techniques to mine the stolen credentials, which would give them the ability to leverage the credentials for targeted attacks. The situation also underscores just how effective phishing still is at hooking victims, he says. The attackers used messages disguised as emails about a variety of topics, with subject lines such as "Purchase Order" and "Inquiry." In addition to the applications mentioned above, the attackers are also targeting credentials for Skype, Amazon, LinkedIn, Google, Yahoo, Hotmail, Rediff, and banks.

Navaraj blogged:

NightHunter is one the more unique campaigns we have researched at Cyphort due to the footprint and complex data collection models it exhibits, furthermore the use of low-signal evasion it is leveraging such as webmail for data exfiltration points to much larger end-goal.

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