LITTLELAMB.WOOLTEA can check the type of Ivanti VPN device it is running on by executing first_run() to identify the first four bytes of the motherboard serial number.2
tool
LITTLELAMB.WOOLTEA S1121
- Type
- malware
- Platform
- Network Devices
- Created
- 13 March 2024
- Last modified
- 15 April 2025
LITTLELAMB.WOOLTEA is a backdoor that was used by UNC5325 during Cutting Edge to deploy malware on targeted Ivanti Connect Secure VPNs and to establish persistence across system upgrades and patches.[1]
7
Techniques33rd pct
4
Tactics32nd pct
0
Threat groupsNone recorded
1
Campaignunranked
Enterprise ATT&CK only. Any Mobile or ICS rows on the same ATT&CK page are not carried.
MITRE reference S1121
LITTLELAMB.WOOLTEA can monitor for system upgrade events by checking for the presence of /tmp/data/root/dev.3
LITTLELAMB.WOOLTEA has the ability to function as a SOCKS proxy.4
LITTLELAMB.WOOLTEA can function as a stand-alone backdoor communicating over the /tmp/clientsDownload.sock socket.5
LITTLELAMB.WOOLTEA can initialize itself as a daemon to run persistently in the background.6
LITTLELAMB.WOOLTEA can append malicious components to the tmp/tmpmnt/bin/samba_upgrade.tar archive inside the factory reset partition in attempt to persist post reset.7
Standing S1121
Reach is how much of ATT&CK this tool touches. Coverage is how well defended each thing it does is, as a median per technique rather than a total — a total would just restate the reach. Each figure is ranked against all 825 ATT&CK software entries only where that population actually spreads. Where most of the population shares one value, a percentile would rank the tie instead of the entity, so the raw value is shown and no rank is claimed.
Reach
Techniques733rd pct
33rd percentile · 67% of 825 ATT&CK software entries have more Enterprise techniques.
Tactics432nd pct
32nd percentile · 68% of 825 ATT&CK software entries have more tactics spanned.
Threat groups061% tie · 22 values
61% of the population shares a single value across only 22 distinct values, so a percentile here would rank the tie, not the entity.
Campaign185% tie · 8 values
85% of the population shares a single value across only 8 distinct values, so a percentile here would rank the tie, not the entity.
Coverage
Rules / technique19med42nd pct
42nd percentile · 58% of 825 ATT&CK software entries have more detection rules per technique.
Tests / technique0med
Detection coverage S1121
148 distinct rules cover the 7 techniques recorded for this tool. The 152 technique-to-rule mappings resolve to 148 distinct rules, because one rule can cover several techniques. 98 Sigma · 50 Splunk.
7 covered by at least one rule148 distinct rules in total
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