Connect with us

Hi, what are you looking for?



Dridex/Locky Operator Uses New RAT in Recent Campaigns

The threat actor responsible for large Dridex and Locky distribution campaigns in the past has been using a brand new backdoor in attacks over the past couple of months, Proofpoint reports. 

The threat actor responsible for large Dridex and Locky distribution campaigns in the past has been using a brand new backdoor in attacks over the past couple of months, Proofpoint reports. 

Tracked by Proofpoint as TA505, the adversary has been distributing a new backdoor named ServHelper since November 2018, and also serving the FlawedGrace malware to its victims. The attacks hit banks, retail businesses, and restaurants. 

The ServHelper malware, the researchers say, has two variants, one designed to provide remote desktop capabilities to the attackers, and another primarily designed as a downloader. This second variant of the malware was observed serving the FlawedGrace remote access Trojan, Proofpoint’s security researchers report. 

The first campaign delivering ServHelper was observed on November 9 and featured only thousands of email messages. Mainly targeting financial institutions, the attack used Microsoft Word or Publisher attachments containing malicious macros that would download and execute the malware. 

A second campaign was observed on November 15, featuring tens of thousands of messages and targeting the retail industry, in addition to financial institutions. The campaign featured Microsoft “.doc”, “.pub”, or “.wiz” attachments that attempted to download the downloader version of ServHelper. 

A third attack, observed on December 13, targeted retail and financial services customers with Word attachments with embedded malicious macros, PDF attachments with URLs linking to a fake page, and direct URLs to a ServHelper downloader executable. As part of this campaign, the malware also attempted to download and execute the FlawedGrace RAT.

ServHelper is written in Delphi and appears to be under active development, with new commands and functions being added to it with each new campaign. 

Advertisement. Scroll to continue reading.

The backdoor variant of the malware has more features and focuses on setting up reverse SSH tunnels to facilitate access to the compromised host via Remote Desktop Protocol (RDP), which allows the attackers to hijack legitimate user accounts. The downloader variant lacks both the tunneling and hijacking functionality.

ServHelper uses HTTP protocol on port 443 (HTTPS) and, less frequently, port 80 (HTTP), to communicate with the command and control (C&C) server. 

The security researchers observed in the malware commands to implement keep-alive functionality, set a reverse SSH tunnel, set a sleep timeout, copy Firefox profile, copy Chrome profiles, kill the SSH tunnel for a particular remote port, get a list of active SSH tunnels, kill all SSH tunnel processes, execute shell command, fetch and run an executable, remove itself from the machine, load DLLs, hijack a user account, and set up an “alerting” mechanism.

The FlawedGrace RAT is written in C++, is very large, makes extensive use of object-oriented and multithreaded programming techniques, and contains support for a multitude of commands. The malware was initially discovered in November 2017, but hasn’t been observed in active campaigns until the recent ServHelper campaigns. 

The malware uses a complicated binary protocol for its C&C and can use a configurable port for communications, yet the observed samples have used port 443. Observed communication includes an initial beacon from the infected system, a key verification message from the system, a key exchange message from the C&C server, and a message containing various system and malware information.

“Threat actor TA505 is both consistent and prolific. When the group distributes new malware, it may be a blip (like Bart ransomware, which was only distributed for one day in 2016) or like Locky ransomware it may become the dominant strain of malware in the wild,” Proofpoint concludes. 

Related: Phishing Campaign Delivers FlawedAmmyy, RMS RATs

Related: Dridex/Locky Operators Unleash New Malware in Recent Attack

Written By

Ionut Arghire is an international correspondent for SecurityWeek.

Click to comment

Daily Briefing Newsletter

Subscribe to the SecurityWeek Email Briefing to stay informed on the latest threats, trends, and technology, along with insightful columns from industry experts.

SecurityWeek’s Threat Detection and Incident Response Summit brings together security practitioners from around the world to share war stories on breaches, APT attacks and threat intelligence.


Securityweek’s CISO Forum will address issues and challenges that are top of mind for today’s security leaders and what the future looks like as chief defenders of the enterprise.


Expert Insights

Related Content


The changing nature of what we still generally call ransomware will continue through 2023, driven by three primary conditions.


Luxury retailer Neiman Marcus Group informed some customers last week that their online accounts had been breached by hackers.


As it evolves, web3 will contain and increase all the security issues of web2 – and perhaps add a few more.


A recently disclosed vBulletin vulnerability, which had a zero-day status for roughly two days last week, was exploited in a hacker attack targeting the...


Satellite TV giant Dish Network confirmed that a recent outage was the result of a cyberattack and admitted that data was stolen.


Zendesk is informing customers about a data breach that started with an SMS phishing campaign targeting the company’s employees.

Artificial Intelligence

The release of OpenAI’s ChatGPT in late 2022 has demonstrated the potential of AI for both good and bad.

Artificial Intelligence

The degree of danger that may be introduced when adversaries start to use AI as an effective weapon of attack rather than a tool...