T1566.001sub-technique of T1566 Phishing
Spearphishing Attachment
Linux · macOS · Windows2 pieces on this siteT1566.001 on attack.mitre.org
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.
If this is happening now
Checklists and playbooks to open while the alert is still live.
A user reported a phishing email
Somebody forwarded a message to the security mailbox, or clicked the report button.
Practise it
Labs, timelines, evidence packs and tabletop scenarios to work before you need to.
Guided lab: nine hours at Northwind Freight, from lure to scheduled task
A constructed intrusion written as a DFIR report. You get the same artifacts an analyst gets on day one, in the order they arrive, and you build the timeline yourself. The company is fictional; the techniques, event IDs and analytic reasoning are not.
how MITRE says to see it
Detection Strategy for Spearphishing Attachment across OS Platforms
- Detection of spearphishing attachments by correlating suspicious email delivery with subsequent file creation and abnormal process execution (e.g., Office spawning PowerShell or CMD). Behavior chain includes inbound email metadata → attachment stored on disk → process execution → outbound network activity.
- Phishing attachments executed on Linux systems are detected by linking email logs to file creation in mail directories and subsequent suspicious process execution. Look for unexpected binaries or scripts spawned from user mail directories and anomalous outbound network activity.
- Phishing attachment detection on macOS through correlation of Mail app logs, file creation in user directories, and abnormal process execution (e.g., Preview.app or Mail.app spawning Terminal or scripting binaries). Network traffic after attachment interaction is also monitored.
what reduces it
- M1031 Network Intrusion Prevention. Network intrusion prevention systems and systems designed to scan and remove malicious email attachments can be used to block activity.
- 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.
- 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.
- 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.