When it comes to malware, email still reigns supreme as the delivery mechanism of choice. The reasoning is simple: It's cheap, it's easily spoofed, and recipients are accustomed to getting messages from various sources. That means when a new attack is found, there's a good possibility that it will spread successfully.
Researchers at Barracuda Networks found, through analyzing attacks on its customer network, a new Quant Loader Trojan campaign using Samba shares as a mechanism - rather than the more common http:// protocol. The result could be a new wave of ransomware attempts, a new round of keystroke loggers, or worse.
The new campaign has similarities to the FlawedAmmyy RAT campaign identified by Proofpoint several weeks ago. In both campaigns, the file:// URL prefix is used to trigger a file download via either SMB protocol or Samba. According to Fleming Shi, senior vice president of advanced technology at Barracuda, this mechanism has several benefits to the attacker when compared to traditional Web downloads.
First, because the URL is malformed and doesn't involve the http:// prefix, it isn't flagged by many defense systems as malicious. "So when they actually analyzed the file, analyzed the behavior, they found it not malicious because the URL was not active," Shi says. "At a later date they'll activate the URL, do the secondary download, and launch the attack."
Quant Loader itself is a Trojan that can be used to distribute a variety of malware payloads, including ransomware and password stealers. It is sold on underground forums and allows the user to configure the payload(s) upon infection using a management panel.
Stephen Boyer, CTO and co-founder of Bitsight, says that it's no wonder that criminals are still using email as a primary attack vector for malware. "I can send you a message without any previous relationship, or knowledge, or authentication scheme," he says. "So that's that's why it's been so effective."
In spite of the potential danger, email is still the most critical messaging form used by business, so there's no real option that includes simply not looking at, opening, or responding to email.
This latest campaign has not limited itself to a single malware payload, Shi says, so it can't be assumed to all be from a single source. In addition, he says there's a characteristic of this campaign that made it especially interesting to researchers.
"We believe the sophistication in this is the ability to alter the packaging at a pretty rapid pace," Shi says. "And also, this wasn't just one day and they went away - they actually kept going."
He says he and his team saw the campaign repeated over more than three weeks, with evidence of its evolution within that timeframe.
Unlike some recent malware outbreaks that have been geographically targeted, Shi says that this latest campaign has had targets all over the UK and North America. The one constant, he says, is English used as the language in the email, though that could easily be changed in future attacks.
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