Dark Reading is part of the Informa Tech Division of Informa PLC

This site is operated by a business or businesses owned by Informa PLC and all copyright resides with them.Informa PLC's registered office is 5 Howick Place, London SW1P 1WG. Registered in England and Wales. Number 8860726.

Attacks/Breaches

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.
Data Privacy Protections for the Most Vulnerable -- Children
Dimitri Sirota, Founder & CEO of BigID,  10/17/2019
Sodinokibi Ransomware: Where Attackers' Money Goes
Kelly Sheridan, Staff Editor, Dark Reading,  10/15/2019
Tor Weaponized to Steal Bitcoin
Dark Reading Staff 10/18/2019
Register for Dark Reading Newsletters
White Papers
Video
Cartoon
Current Issue
7 Threats & Disruptive Forces Changing the Face of Cybersecurity
This Dark Reading Tech Digest gives an in-depth look at the biggest emerging threats and disruptive forces that are changing the face of cybersecurity today.
Flash Poll
2019 Online Malware and Threats
2019 Online Malware and Threats
As cyberattacks become more frequent and more sophisticated, enterprise security teams are under unprecedented pressure to respond. Is your organization ready?
Twitter Feed
Dark Reading - Bug Report
Bug Report
Enterprise Vulnerabilities
From DHS/US-CERT's National Vulnerability Database
CVE-2019-18218
PUBLISHED: 2019-10-21
cdf_read_property_info in cdf.c in file through 5.37 does not restrict the number of CDF_VECTOR elements, which allows a heap-based buffer overflow (4-byte out-of-bounds write).
CVE-2019-18217
PUBLISHED: 2019-10-21
ProFTPD before 1.3.6b and 1.3.7rc before 1.3.7rc2 allows remote unauthenticated denial-of-service due to incorrect handling of overly long commands because main.c in a child process enters an infinite loop.
CVE-2019-16862
PUBLISHED: 2019-10-21
Reflected XSS in interface/forms/eye_mag/view.php in OpenEMR 5.x before 5.0.2.1 allows a remote attacker to execute arbitrary code in the context of a user's session via the pid parameter.
CVE-2019-17409
PUBLISHED: 2019-10-21
Reflected XSS exists in interface/forms/eye_mag/view.php in OpenEMR 5.x before 5.0.2.1 ia the id parameter.
CVE-2019-10715
PUBLISHED: 2019-10-21
There is Stored XSS in Verodin Director before 3.5.4.0 via input fields of certain tooltips, and on the Tags, Sequences, and Actors pages.