Phishing: Spearphishing Attachment

ID: T1566.001
Tactics: TA0001 Initial Access
Sub-technique of: T1566 Phishing
Platforms: Linux, macOS, Windows
Data sources: Application Log Content, File Creation, Process Creation, Network Connection Creation, Network Traffic Flow
Source: attack.mitre.org
MITRE last modified: 12 Sep 2026

Adversaries may send spearphishing emails with a malicious attachment in an attempt to gain access to victim systems. Spearphishing attachment is a specific variant of spearphishing. Spearphishing attachment is different from other forms of spearphishing in that it employs the use of malware attached to an email. 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 and usually rely upon User Execution to gain execution.^[3] Spearphishing may also involve social engineering techniques, such as posing as a trusted source.

There are many options for the attachment such as Microsoft Office documents, executables, PDFs, or archived files. Upon opening the attachment (and potentially clicking past protections), the adversary's payload exploits a vulnerability or directly executes on the user's system. The text of the spearphishing email usually tries to give a plausible reason why the file should be opened, and may explain how to bypass system protections in order to do so. The email may also contain instructions on how to decrypt an attachment, such as a zip file password, in order to evade email boundary defenses. Adversaries frequently manipulate file extensions and icons in order to make attached executables appear to be document files, or files exploiting one application appear to be a file for a different one.

Detection

DET0236 Detection Strategy for Spearphishing Attachment across OS Platforms
Data components: Application Log Content, File Creation, Process Creation, Network Connection Creation, Network Traffic Flow

Mitigations (7)

M1017 User Training: Users can be trained to identify social engineering techniques and spearphishing emails.
M1018 User Account Management: Apply user account management principles to limit permissions for accounts interacting with email attachments, ensuring that only necessary accounts have the ability to open or execute files. Restricting account privileges reduces the potential impact of malicious attachments by preventing unauthorized execution or spread of malware within the environment.
M1021 Restrict Web-Based Content: Block unknown or unused attachments by default that should not be transmitted over email as a best practice to prevent some vectors, such as .scr, .exe, .pif, .cpl, etc. Some email scanning devices can open and analyze compressed and encrypted formats, such as zip and rar that may be used to conceal malicious attachments.
M1031 Network Intrusion Prevention: Network intrusion prevention systems and systems designed to scan and remove malicious email attachments can be used to block activity.
M1047 Audit: Enable auditing and monitoring for email attachments and file transfers to detect and investigate suspicious activity. Regularly review logs for anomalies related to attachments containing potentially malicious content, as well as any attempts to execute or interact with these files. This practice helps identify spearphishing attempts before they can lead to further compromise.
M1049 Antivirus/Antimalware: Anti-virus can also automatically quarantine suspicious files.
M1054 Software Configuration: Use anti-spoofing and email authentication mechanisms to filter messages based on validity checks of the sender domain (using SPF) and integrity of messages (using DKIM). Enabling these mechanisms within an organization (through policies such as DMARC) may enable recipients (intra-org and cross domain) to perform similar message filtering and validation.^[1]^[2]

Phishing: Spearphishing Attachment

Detection

Mitigations (7)

Groups (79)

Software (62)

References