Network Connection Initiated To Cloudflared Tunnels Domains

Severity: medium
Author: Kamran Saifullah, Nasreddine Bencherchali (Nextron Systems)
Source: upstream

Detects network connections to Cloudflared tunnels domains initiated by a process on the system. Attackers can abuse that feature to establish a reverse shell or persistence on a machine.

MITRE ATT&CK coverage

Tactic	Techniques
Command & Control	`T1572` Protocol Tunneling
Exfiltration	`T1567` Exfiltration Over Web Service

Event coverage

Provider	Event ID	Title
Sysmon	3	Network connection

Stages and Predicates

Stage 1: `selection`

or:
DestinationHostname|endswith: .v2.argotunnel.com
DestinationHostname|endswith: protocol-v2.argotunnel.com
DestinationHostname|endswith: trycloudflare.com
DestinationHostname|endswith: update.argotunnel.com
Initiated: true

Indicators

Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.