Attacks/Breaches

10/31/2018
03:30 PM
Connect Directly
Google+
Twitter
RSS
E-Mail
50%
50%

Pervasive Emotet Botnet Now Steals Emails

Researchers discover new cyber-spying function in the persistent malware operation's arsenal.

After a month of laying low, the ubiquitous Emotet botnet has come alive again with a new module that siphons email messages from machines infected by the malware.

Hundreds of thousands of victim machines across 170 countries are now likely outfitted with the email-stealing component of the malware, according to research by Kryptos Logic. The US is by far the biggest victim to date, with somewhere between 40,000 and 50,000 infected machines.

The email-stealing module represents a dramatic shift for the malware, adding a cyber espionage and reconnaissance element to it. "We haven't observed this aggressive [behavior] in nonstate [hackers before]," says Salim Neino, CEO of Kryptos Logic. "They were a bit quiet for the month, and then they came out with this new email mass exfiltration [module]."  

Emotet has been high on the radar screen of the US Department of Homeland Security's US-CERT, which this summer posted a detailed alert on how to detect and defend against the malware, a sophisticated Trojan that has evolved significantly in its four years of life. Emotet has been used to drop ransomware on water utilities and other high-profile organizations. In addition, it is one of the most expensive malware threats to hit state and local governments, with costs of up to $1 million per incident.

The botnet has been evolving into more of an attack-for-hire service since this summer. It typically spreads via rigged email attachments and infected URLs. Once it executes on a machine, it spreads via the EternalBlue vulnerability that acts as a worm, spreading via hacked Windows domain credentials and then spreading widely throughout an infected organization.

Emotet's new email-stealing function could be a value add of sorts for other hacker groups who want to hire the botnet service, Neino notes, or it could indicate that Emotet has teamed with a more aggressive hacking group.

Symantec calls the cybercrime group behind Emotet "Mealybug." "Most recently, Mealybug appears to have expanded its operations to primarily become a distributor of threats for other attack groups," Symantec said in July blog post about the botnet. "It appears to have changed its business model in recent times, evolving from targeting banking customers in Europe to using its infrastructure to act as a global packing and delivery service for other threat actors."

Emotet, which previously stole email contacts from victims via an Outlook Messaging API module, employs the built-in Windows MAPI function. It can grab emails in an inbox as far back as 180 days, according to Kryptos' discovery. "It's basically moving from semi-personalized attacks in spam ... to more personalized and maintainable attacks," Neino says.

It works like this: The email-stealing module scans the emails of a victim and saves the results in a temporary file, which ultimately gets transmitted to the botnet command-and-control server if it's larger than 116 bytes. If it's smaller, the Windows dynamic link library (DLL) module reads the file, according to Kryptos. The company posted a blog today with the technical details.

The best defense against Emotet is strong endpoint security and threat intelligence, Neino says, including his firm's free TellTale service, where organizations can type in their IP address to see whether they are infected with Emotet or other botnet malware, including WannaCry.

In addition to the usual patching and layered security, email certification measures, and other typical practices, restricting inbound SMB traffic is another defense against Emotet, according to US-CERT.

"Emotet is one of the most active – and now most aggressive – groups out there maintaining a foothold in distributing malware," Neino says.

Related Content:

Black Hat Europe returns to London Dec 3-6 2018  with hands-on technical Trainings, cutting-edge Briefings, Arsenal open-source tool demonstrations, top-tier security solutions and service providers in the Business Hall. Click for information on the conference and to register.

Kelly Jackson Higgins is Executive Editor at DarkReading.com. She is an award-winning veteran technology and business journalist with more than two decades of experience in reporting and editing for various publications, including Network Computing, Secure Enterprise ... View Full Bio

Comment  | 
Print  | 
More Insights
Comments
Newest First  |  Oldest First  |  Threaded View
Russia Hacked Clinton's Computers Five Hours After Trump's Call
Robert Lemos, Technology Journalist/Data Researcher,  4/19/2019
Tips for the Aftermath of a Cyberattack
Kelly Sheridan, Staff Editor, Dark Reading,  4/17/2019
Register for Dark Reading Newsletters
White Papers
Video
Cartoon
Current Issue
5 Emerging Cyber Threats to Watch for in 2019
Online attackers are constantly developing new, innovative ways to break into the enterprise. This Dark Reading Tech Digest gives an in-depth look at five emerging attack trends and exploits your security team should look out for, along with helpful recommendations on how you can prevent your organization from falling victim.
Flash Poll
Twitter Feed
Dark Reading - Bug Report
Bug Report
Enterprise Vulnerabilities
From DHS/US-CERT's National Vulnerability Database
CVE-2019-11378
PUBLISHED: 2019-04-20
An issue was discovered in ProjectSend r1053. upload-process-form.php allows finished_files[]=../ directory traversal. It is possible for users to read arbitrary files and (potentially) access the supporting database, delete arbitrary files, access user passwords, or run arbitrary code.
CVE-2019-11372
PUBLISHED: 2019-04-20
An out-of-bounds read in MediaInfoLib::File__Tags_Helper::Synched_Test in Tag/File__Tags.cpp in MediaInfoLib in MediaArea MediaInfo 18.12 leads to a crash.
CVE-2019-11373
PUBLISHED: 2019-04-20
An out-of-bounds read in File__Analyze::Get_L8 in File__Analyze_Buffer.cpp in MediaInfoLib in MediaArea MediaInfo 18.12 leads to a crash.
CVE-2019-11374
PUBLISHED: 2019-04-20
74CMS v5.0.1 has a CSRF vulnerability to add a new admin user via the index.php?m=Admin&c=admin&a=add URI.
CVE-2019-11375
PUBLISHED: 2019-04-20
Msvod v10 has a CSRF vulnerability to change user information via the admin/member/edit.html URI.