Attacks/Breaches

4/17/2018
09:30 AM
100%
0%

New Malware Adds RAT to a Persistent Loader

A newly discovered variant of a long-known malware loader adds the ability to control the victim from afar.

VBScript has long been an attack vector that could bring malicious software to an infected machine. But what if it could do more? What if VBScript could open a door to allow a PHP application access that would take control of a computer, making it part of a botnet? That's precisely the scenario in a newly described campaign called ARS VBS Loader, a variant of a popular downloader called SafeLoader VBS.

The new ARS VBS Loader, described by researchers at Flashpoint, downloads malware and provides remote-control access to a botnet controller, making it both a malware loader and a RAT, or remote access trojan. Paul Burbage, senior malware researcher at Flashpoint, says that he first noticed the new loader variant being sold on Russian malware sites in December 2017. It was, he says, being sold as a FUD ASPC (VBScript) loader — with "FUD" in this case meaning "fully undetectable."

Burbage says that there are two characteristics of ARS VBS that make it highly unusual. The first is persistence; the second is the remote access capability.

"The persistence mechanism for this loader is pretty unique," Burbage says. "It reports the statistics on its success back to the command and control server and is able to download additional malware from the server." As a result, he says that the threat actors can switch things up, changing attacks and profiles on the fly once the infection is in place.

One of the things that the persistent loader can do is receive additional commands. That's unusual for a loader because, Burbage says, "They tend not to have any command and control within the script." He say ARS VBS was authored with the intent for it to be the RAT, and that combines with the persistence mechanism to make it especially dangerous.

Asked whether the botnet to which ARS VBS seems to be recruiting systems is dangerous, Burbage says that it's far from the worst botnet he's seen. "I'm not sure how effective that would be in the wild because it utilizes a PHP POST Flood," he says, adding, "Most web sites easily defeat those."

So far, this new loader variant is being spread by relatively unsophisticated means. "Most of the initial infection records we see are massive shotgun spam campaigns that aren't carefully targeted," Burbage says, noting that they succeed because users are still clicking on attachments coming from unknown sensors and VBScript payloads are still getting past anti-malware security systems. "It's really hard to tell the difference between legitimate VBScript files that network admins might use for legitimate admin duties, and malware," Burbage says.

"VBScript is baked in, or supported out of the box, with every Windows system," he explains. "There might be a way to turn it off within an organization, but you'd lose the ability to perform authorized tasks."

Related content:

Interop ITX 2018

Join Dark Reading LIVE for a two-day Cybersecurity Crash Course at Interop ITX. Learn from the industry’s most knowledgeable IT security experts. Check out the agenda here. Register with Promo Code DR200 and save $200.

Curtis Franklin Jr. is Senior Editor at Dark Reading. In this role he focuses on product and technology coverage for the publication. In addition he works on audio and video programming for Dark Reading and contributes to activities at Interop ITX, Black Hat, INsecurity, and ... View Full Bio

Comment  | 
Print  | 
More Insights
Comments
Newest First  |  Oldest First  |  Threaded View
mmckeown
50%
50%
mmckeown,
User Rank: Apprentice
4/21/2018 | 6:53:35 PM
Great Write Up
Excellent article.  Be interesting what the most effective way to counter the threat.
New Cold Boot Attack Gives Hackers the Keys to PCs, Macs
Kelly Sheridan, Staff Editor, Dark Reading,  9/13/2018
Yahoo Class-Action Suits Set for Settlement
Dark Reading Staff 9/17/2018
RDP Ports Prove Hot Commodities on the Dark Web
Kelly Sheridan, Staff Editor, Dark Reading,  9/17/2018
Register for Dark Reading Newsletters
White Papers
Video
Cartoon Contest
Write a Caption, Win a Starbucks Card! Click Here
Latest Comment: This comment is waiting for review by our moderators.
Current Issue
Flash Poll
How Data Breaches Affect the Enterprise
How Data Breaches Affect the Enterprise
This report, offers new data on the frequency of data breaches, the losses they cause, and the steps that organizations are taking to prevent them in the future. Read the report today!
Twitter Feed
Dark Reading - Bug Report
Bug Report
Enterprise Vulnerabilities
From DHS/US-CERT's National Vulnerability Database
CVE-2017-3912
PUBLISHED: 2018-09-18
Bypassing password security vulnerability in McAfee Application and Change Control (MACC) 7.0.1 and 6.2.0 allows authenticated users to perform arbitrary command execution via a command-line utility.
CVE-2018-6690
PUBLISHED: 2018-09-18
Accessing, modifying, or executing executable files vulnerability in Microsoft Windows client in McAfee Application and Change Control (MACC) 8.0.0 Hotfix 4 and earlier allows authenticated users to execute arbitrary code via file transfer from external system.
CVE-2018-6693
PUBLISHED: 2018-09-18
An unprivileged user can delete arbitrary files on a Linux system running ENSLTP 10.5.1, 10.5.0, and 10.2.3 Hotfix 1246778 and earlier. By exploiting a time of check to time of use (TOCTOU) race condition during a specific scanning sequence, the unprivileged user is able to perform a privilege escal...
CVE-2018-16515
PUBLISHED: 2018-09-18
Matrix Synapse before 0.33.3.1 allows remote attackers to spoof events and possibly have unspecified other impacts by leveraging improper transaction and event signature validation.
CVE-2018-16794
PUBLISHED: 2018-09-18
Microsoft ADFS 4.0 Windows Server 2016 and previous (Active Directory Federation Services) has an SSRF vulnerability via the txtBoxEmail parameter in /adfs/ls.