At end of the 2021 IRS income tax return deadline in the United States, cybercriminals were leveraging advanced tactics in their phishing kits, which in turn granted them a high delivery success rate of spoofed e-mails with malicious attachments.
On April 18th, 2022, a notable campaign was detected which invested phishing e-mails imitating the IRS, and in particular one of the industry vendors who provide services to government agencies which include e-mailing,
Cybercriminals chose specific seasons when taxpayers are all busy with taxes and holiday preparations, which is why one should be extra cautious at these times.
The impersonated IT services vendor is widely employed by key federal agencies, including the Department of Homeland Security, as well as various state and local government websites in the United States. The detected phishing e-mail alerted victims about outstanding IRS payments, which should be paid via PayPal, and included an HTML attachment which looked like an electronic invoice. Notably, the e-mail has no URLs and was delivered to the victim's mailbox without being tagged as spam. The e-mail was delivered through many "hops" based on the inspected headers, predominantly using network hosts and domains registered in the United States.
It is worth mentioning that none of the affected hosts had previously been 'blacklisted,' nor had any evidence of bad IP or anomalous domain reputation at the time of identification. The bogus IRS invoice's HTML attachment contains JS-based obfuscation code. Further investigation revealed embedded scenarios which detected the victim's IP (using the GEO2IP module, which was placed on a third-party WEB-site), most likely to choose targets or filter by region.
After the user views the HTML link, the phishing script shall prompt the user to enter personal credentials, impersonating the Office 365 authentication process with an interactive form.
The phishing-kit checks access to the victim's e-mail account through IMAP protocol once the user enters personal credentials. The actors were utilizing the "supportmicrohere[.]com" domain relying on the de-obfuscated JS content.
Threat actors most likely tried to imitate Microsoft Technical Support and deceive users by utilizing a domain with similar spelling. The script intercepts the user's credentials and sends them to the server using a POST request. Login and password are sent to the jbdelmarket[.]com script through HTTP POST. A series of scripts to examine the IP address of the victim is hosted on the domain jbdelmarket[.]com. The phishing e-header emails include multiple domain names with SPF and DKIM records.
A Return-Path field in the phishing e-mail was set as another e-mail controlled by the attackers which gather data about e-mails that were not sent properly. The Return-Path specifies how and where rejected emails will be processed, and it is used to process bounces from emails.
