Tax-Related Phishing Scams Delivering TrickBot Trojan

Monday April 15 is Tax Day in the United States – the deadline for submitting 2018 tax returns. Each year in the run up to Tax Day, cybercriminals step up their efforts to obtain users’ tax credentials. In the past few weeks, many tax-related phishing scams have been detected which attempt to install information stealing malware.

One of the main aims of these campaigns is to obtain tax credentials. These are subsequently used to file fraudulent tax returns with the IRS. Tax is refunded to accounts controlled by the attackers, checks are redirected, and a range of other methods are used to obtain the payments.

Attacks on tax professionals are commonplace. If access can be gained to a tax professional’s computer, the tax credentials of clients can be stolen, and fraudulent tax returns can be filed in their names. A single successful attack on a tax professional can see the attacker obtain many thousands of dollars in tax rebates.

There has been the usual high level of tax-related phishing scams during the 2019 tax season and businesses of all types have been targeted. It is not only tax credentials that cybercriminals are after. Many tax-themed phishing scams have been conducted which attempt to install malware and ransomware such as the TrickBot banking Trojan.

The TrickBot banking Trojan is a powerful malware variant which, once installed, can give an attacker full control of an infected computer. The malware is primarily an information stealer. A successful installation on one business computer can allow the attackers to move laterally and spread the malware across the whole network.

The primary purpose of the TrickBot trojan is to steal banking credentials which can be used to make fraudulent wire transfers: however, TrickBot is regularly updated with new features. In addition to stealing banking credentials, the malware can steal VNC. RDP, and PuTTY credentials.

The threat actors behind TrickBot are highly organized and well resourced. More than 2,400 command and control servers are used by the cybercriminal gang and that number continues to grow.

The three new TrickBot malware campaigns were detected since late January by IBM X-Force researchers. Spam email messages are carefully crafted to appear legitimate and look innocuous to business users and appear to have been sent by well-known accounting and payroll firms such as ADP and Paychex.

Spoofed email addresses are commonly used, although in these campaigns, the attackers have used domain squatting. They have registered domains that are very similar to those used by the accounting firms. The domains have transposed letters and slight misspellings to make the email appear to have been sent from a legitimate source. The domains can be highly convincing and, in some cases, are extremely difficult to identify as fake.

The emails are well written and claim to include tax billing records, which are included as attached spreadsheets. The spreadsheets contain malicious macros which, if allowed to run, will download the TrickBot Trojan.

To prevent attacks, several steps should be taken. Macros should be disabled by default on all devices. Prompt patching is required to keep all software and operating systems up to date to prevent vulnerabilities from being exploited.

End users should receive security awareness training and should be taught cybersecurity best practices and how to identify phishing emails. An advanced spam and anti-phishing solution should also be implemented to ensure phishing emails are identified and prevented from reaching end users inboxes. Further, all IoCs and IPs known to be associated with the threat actors should be blocked through spam filtering solutions, firewalls, and web gateways.

The latter is made easy with SpamTitan and WebTitan – TitanHQ’s anti-phishing and web filtering solutions for SMBs.