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Created March 31, 2021 16:36
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Sigma rule for Internal Cleartext Protocol Usage
title: Internal Cleartext Protocol Usage
status: experimental
description: Detects common cleartext procotols from internal endpoints.
author: Josh Brower
logsource:
category: firewall
defintion: Tweak logsource to whichever logsource is used in the local environment ie Zeek Conn.
detection:
internal_ip:
src_ip|startswith:
- '192.168.'
- '10.'
- '172.16.'
- '172.17.'
- '172.18.'
- '172.19.'
- '172.20.'
- '172.21.'
- '172.22.'
- '172.23.'
- '172.24.'
- '172.25.'
- '172.26.'
- '172.27.'
- '172.28.'
- '172.29.'
- '172.30.'
- '172.31.'
cleartext_protocol:
dst_port:
- 20 #FTP Data
- 21 #FTP Control
- 23 #Telnet
- 161 #SNMP
- 162 #SNMP
- 143 #IMAP
- 110 #POP3
- 389 #LDAP
condition: internal_ip and cleartext_protocol
falsepositives:
- Unknown
fields:
- src_ip
level: medium
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