Techniques › T1598 › T1598.002
T1598.002 Spearphishing Attachment
reconnaissance — PRE · attack.mitre.org · JSON
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MITRE detection strategy
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analytics
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Sigma rules tagged attack.t1598.002
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KEV CVEs mapped here
<p>Adversaries may send spearphishing messages with a malicious attachment to elicit sensitive information that can be used during targeting. Spearphishing for information is an attempt to trick targets into divulging information, frequently credentials or other actionable information. Spearphishing for information frequently involves social engineering techniques, such as posing as a source with a reason to collect information (ex: Establish Accounts or Compromise Accounts) and/or sending multiple, seemingly urgent messages.</p><p>All forms of spearphishing are electronically delivered social engineering targeted at a specific individual, company, or industry. In this scenario, adversaries attach a file to the spearphishing email. In some cases, they may rely upon the recipient populating information, then returning the file. The text of the spearphishing email usually tries to give a plausible reason why the file should be filled-in, such as a request for information from a business associate. In other cases, adversaries may leverage techniques such as HTML Smuggling to harvest user credentials via fake login portals.</p><p>Adversaries may also use information from previous reconnaissance efforts (ex: Search Open Websites/Domains or Search Victim-Owned Websites) to craft persuasive and believable lures.</p>
KEV CVEs mapped to this technique · CTID Mappings Explorer
| CVE | Vendor / product | Mapping type | State | Added |
|---|---|---|---|---|
| CVE-2021-33739 | Microsoft Windows | exploitation technique | Mapped | 2021-11-03 |
Detection strategy · ATT&CK Enterprise v19.2
- DET0865 Detection of Spearphishing Attachment v1.0
AN1997 PREMonitor network data for uncommon data flows. Processes utilizing the network that do not normally have network communication or have never been seen before are suspicious. Monitor for suspicious email activity, such as numerous accounts receiving messages from a single unusual/unknown sender. Filtering based on DKIM+SPF or header analysis can help detect when the email sender is spoofed. Monitor and analyze traffic patterns and packet inspection associated to protocol(s) that do not follow the expected protocol standards and traffic flows (e.g extraneous packets that do not belong to established flows, gratuitous or anomalous traffic patterns, anomalous syntax, or structure). Consider correlation with process monitoring and command line to detect anomalous processes execution and command line arguments associated to traffic patterns (e.g. monitor anomalies in use of files that do not normally initiate connections for respective protocol(s)).
Sigma rules · SigmaHQ da9bb07d64, tag attack.t1598.002
Author: Joseph Kamau
· 2025-12-05 · logsource: product=windows category=process_creation · 538c5851-8c03-4724-8ec4-623bc7aadaea
Detects web browser process opening an HTML file from a user's Downloads folder.
This behavior is could be associated with phishing attacks where threat actors send HTML attachments to users.
When a user opens such an attachment, it can lead to the execution of malicious scripts or the download of malware.
During investigation, analyze the HTML file for embedded scripts or links, check for any subsequent downloads or process executions, and investigate the source of the email or message containing the attachment.