Detection rules › Sublime MQL

Spam: SMTP & Proxy Communications in Email Body

Severity
medium
Type
rule
Source
github.com/sublime-security/sublime-rules

An email containing SMTP and Proxy (socks5) command and control information within the body of the message.

Threat classification

Sublime's own taxonomy (not MITRE ATT&CK).

CategoryValues
Attack typesSpam
Tactics and techniquesFree email provider

Event coverage

Rule body MQL

type.inbound
and length(attachments) == 0
and 1 < length(body.links) < 5
and regex.icontains(body.current_thread.text,
                    '(?:\:socks5:|::127.0.0.1:1080|:0:127.0.0.1:1080)'
)

Detection logic

Scope: inbound message.

An email containing SMTP and Proxy (socks5) command and control information within the body of the message.

  1. inbound message
  2. length(attachments) is 0
  3. all of:
    • length(body.links) > 1
    • length(body.links) < 5
  4. body.current_thread.text matches '(?:\\:socks5:|::127.0.0.1:1080|:0:127.0.0.1:1080)'

Inspects: body.current_thread.text, body.links, type.inbound. Sensors: regex.icontains.

Indicators matched (1)

FieldMatchValue
regex.icontainsregex(?:\:socks5:|::127.0.0.1:1080|:0:127.0.0.1:1080)