sublimelowRule

Link: Direct download of executable file

Detects messages containing links that directly download executable (.exe) files, with a limited number of distinct links that are either unrelated to the sender's domain or not in the top 10k most popular websites.

MITRE ATT&CK

T1566.001 T1204.002 T1486 T1036 T1027

defense-evasion

Detection Query

type.inbound
// the link leads to a direct download of an EXE file
and any(body.current_thread.links,
        strings.iends_with(.href_url.url, '.exe')
        and not .href_url.domain.root_domain == sender.email.domain.root_domain
        and not (
          .href_url.domain.root_domain in $tranco_10k
          // if the link is to a free_file_hosts that is in tracno, still match (bitbucket, githubusercontent, etc.)
          and not .href_url.domain.root_domain in $free_file_hosts
        )
)

Data Sources

Email MessagesEmail HeadersEmail Attachments

Platforms

Tags

Attack surface reduction

Raw Content

name: "Link: Direct download of executable file"
description: "Detects messages containing links that directly download executable (.exe) files, with a limited number of distinct links that are either unrelated to the sender's domain or not in the top 10k most popular websites."
type: "rule"
severity: "low"
false_positives:
  - "It is possible for this to match benign samples such as surface advisories related to executable file attachments and direct links to download applications."
source: |
  type.inbound
  // the link leads to a direct download of an EXE file
  and any(body.current_thread.links,
          strings.iends_with(.href_url.url, '.exe')
          and not .href_url.domain.root_domain == sender.email.domain.root_domain
          and not (
            .href_url.domain.root_domain in $tranco_10k
            // if the link is to a free_file_hosts that is in tracno, still match (bitbucket, githubusercontent, etc.)
            and not .href_url.domain.root_domain in $free_file_hosts
          )
  )

tags:
  - "Attack surface reduction"
attack_types:
  - "Malware/Ransomware"
tactics_and_techniques:
  - "Evasion"
detection_methods:
  - "Sender analysis"
  - "URL analysis"
id: "dbbfd077-ec96-5f5a-a234-c45a6bae92c8"