Security Experts:

Connect with us

Hi, what are you looking for?

SecurityWeekSecurityWeek

Malware & Threats

Tofsee Malware Distribution Switched From Exploit Kit to Spam

The RIG exploit kit recently stopped distributing Tofsee and cybercriminals have decided to use the botnet’s own spamming capabilities to deliver the malware, Cisco’s Talos team reported on Thursday.

The RIG exploit kit recently stopped distributing Tofsee and cybercriminals have decided to use the botnet’s own spamming capabilities to deliver the malware, Cisco’s Talos team reported on Thursday.

Tofsee, a multi-purpose malware that has been around since 2013, allows cybercriminals to conduct various activities, including click fraud, cryptocurrency mining, DDoS attacks and sending spam.

Up until June 2016, cybercriminals distributed the malware using the RIG exploit kit and malvertising campaigns. Then, after the notorious Angler exploit kit disappeared from the scene, cybercriminals started leveraging RIG to deliver other payloads, which experts believe might have been more profitable.

After RIG stopped delivering Tofsee, cybercriminals turned to email spam campaigns to infect computers. Typically, the Tofsee botnet has been used to send spam emails advertising adult dating and pharmaceutical websites. However, in August, researchers noticed that the spam messages had changed and started delivering Tofsee malware downloaders.

The volume of these spam emails has gradually increased since mid-August, reaching more than 2,000 messages on some days in September, Cisco Talos reported.

The spammy emails are adult-themed and they purport to come from women in Russia and Ukraine. Recipients are instructed to download and open the ZIP archive attached to the messages as it allegedly contains pictures of the sender.

Instead of pictures, the archive contains an obfuscated JavaScript file that includes a WScript downloader designed to fetch and run an executable from a remote server controlled by the attacker. Once the file is executed, the system becomes infected with Tofsee.

The malware connects to various SMTP relays, which it uses to send spam emails. The threat also initiates HTTP connections as it simulates clicking on ads as part of its click fraud mechanism.

Since the demise of Angler, the RIG exploit kit has been used to deliver the SmokeLoader (aka Dofoil) backdoor and other malware. Its developers have been working on improving the kit with new exploits and command and control (C&C) patterns that could help it evade detection.

Earlier this week, researchers reported that RIG had taken the place of Neutrino in a massive malvertising campaign that delivered CryptMIC ransomware. The campaign had previously used Neutrino, which took the leading position after Angler disappeared.

Related: Cisco Targets RIG Exploit Kit

Related: Kaspersky Confirms Lurk Gang Developed Angler Exploit Kit

Written By

Eduard Kovacs (@EduardKovacs) is a contributing editor at SecurityWeek. He worked as a high school IT teacher for two years before starting a career in journalism as Softpedia’s security news reporter. Eduard holds a bachelor’s degree in industrial informatics and a master’s degree in computer techniques applied in electrical engineering.

Click to comment

Expert Insights

Related Content

Malware & Threats

Microsoft plans to improve the protection of Office users by blocking XLL add-ins from the internet.

Cybercrime

CISA, NSA, and MS-ISAC issued an alert on the malicious use of RMM software to steal money from bank accounts.

Cybercrime

Chinese threat actor DragonSpark has been using the SparkRAT open source backdoor in attacks targeting East Asian organizations.

Malware & Threats

Norway‎-based DNV said a ransomware attack on its ship management software impacted 1,000 vessels.

Application Security

Electric car maker Tesla is using the annual Pwn2Own hacker contest to incentivize security researchers to showcase complex exploit chains that can lead to...

Malware & Threats

Cybercrime in 2017 was a tumultuous year "full of twists and turns", with new (but old) infection methods, a major return to social engineering,...

Malware & Threats

Fortinet warned of three malicious PyPI packages containing code that fetches the Wacatac trojan and information stealer.

Cybercrime

The recent ransomware attack targeting Rackspace was conducted by a cybercrime group named Play using a new exploitation method, the cloud company revealed this...