Spearphishing Link

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Spearphishing Link
Technique
ID T1192
Tactic Initial Access
Platform Linux, Windows, macOS
Data Sources Packet capture, Web proxy, Email gateway, Detonation chamber, SSL/TLS inspection, DNS records, Mail server
CAPEC ID CAPEC-163

Spearphishing with a link is a specific variant of spearphishing. It is different from other forms of spearphishing in that it employs the use of links to download malware contained in email, instead of attachment malicious files to the email itself, to avoid defenses that may inspect email attachments.

All forms of spearphishing are electronically delivered social engineering targeted at a specific individual, company, or industry. In this case, the malicious emails contain links. Generally, the links will be accompanied by social engineering text and require the user to actively click or copy and paste a URL into a browser, leveraging User Execution. The visited website may compromise the web browser using an exploit, or the user will be prompted to download applications, documents, zip files, or even executables depending on the pretext for the email in the first place. Adversaries may also include links that are intended to interact directly with an email reader, including embedded images intended to exploit the end system directly or verify the receipt of an email (i.e. web bugs/web beacons).

Examples

  • APT29 has used spearphishing with a link to trick victims into clicking on a link to a zip file containing malicious files. 1
  • APT33 sent spear phishing emails containing links to .hta files.2
  • Elderwood has delivered zero-day exploits and malware to victims via targeted emails containing a link to malicious content hosted on an uncommon Web server.34
  • FIN8 has distributed targeted emails containing links to malicious documents with embedded macros.5
  • Leviathan has sent spearphishing emails with links, often using a fraudulent lookalike domain and stolen branding.6
  • Magic Hound sent shortened URL links over email to victims. The URLs linked to Word documents with malicious macros that execute PowerShells scripts to download Pupy.7
  • Patchwork has used spearphishing with links to deliver files with exploits to initial victims.8

Mitigation

Because this technique involves user interaction on the endpoint, it's difficult to fully mitigate. However, there are potential mitigations. Users can be trained to identify social engineering techniques and spearphishing emails with malicious links. Other mitigations can take place as User Execution occurs.

Detection

URL inspection within email (including expanding shortened links) can help detect links leading to known malicious sites. Detonation chambers can be used to detect these links and either automatically go to these sites to determine if they're potentially malicious, or wait and capture the content if a user visits the link.

Because this technique usually involves user interaction on the endpoint, many of the possible detections for Spearphishing Link take place once User Execution occurs.