Cybersecurity researchers are calling attention to phishing campaigns that now impersonate many well-known popular brands. These attackers frequently use PDF attachments as a primary vehicle for delivering their deceptive and malicious content. This method exploits the trust people have in popular brands to initiate malicious actions against them. An analysis revealed Microsoft and Docusign as the most impersonated brands in emails with various PDF attachments.
Two popular social engineering techniques include callback phishing and the malicious use of embedded QR codes.
Telephone-Oriented Attack Delivery, or TOAD, is another popular social engineering technique used by these threat actors. PDF payloads persuade victims to call adversary-controlled phone numbers to resolve a fake issue or confirm transactions. During the phone call, an attacker masquerades as a legitimate representative to trick and manipulate the victim. They attempt to get the victim to either disclose sensitive information or install malware on their devices. Attackers often use VoIP numbers to remain anonymous and sometimes reuse them for multi-stage social engineering attacks.
Adversaries also extensively use QR codes in their brand impersonation phishing emails, a tactic known as quishing.
Attackers exploit the legitimacy of popular brands to convince users to scan the QR code in the PDF. Scanning the code ultimately redirects the unsuspecting user to a phishing page designed to steal their login credentials. To make phishing emails more evasive, attackers will often exploit otherwise legitimate PDF annotations to hide links. A QR code may link to a legitimate web page while the embedded annotation points to the phishing page.
These tactics are part of a wider trend of attackers abusing legitimate features to bypass standard security. For example, some campaigns capitalize on Microsoft 365’s Direct Send feature to spoof internal company user emails. Emerging research has also found that threat actors are trying to poison large language model AI chatbot responses. They are also using illicit services like Hacklink to manipulate search engine algorithms to prioritize phishing websites. This shows how criminals constantly diversify methods, making defense a significant and ongoing challenge for security teams.
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