06-11-2021 09:42 AM
We are investigating alerts of this DNS signature for x1.c.lencr.org.
I'd expect that a match for a clear text string in a DNS Request that it is very unlikely this is a false detection.
However to get alerts so quickly after this signature creation, suggests we are either very unlucky or a very common public internet resource if causing this fly-by access. Anyone else receiving this threat alert shortly after an apparent WF update.
06-14-2021 10:19 PM
Looks like a false positive to me, I can't see why that particular Let'sEncrypt domain is flagged as malicious.
06-15-2021 04:41 AM
Did you happen to see additional events to x1.c.lencr.org late last evening until early this morning (12:33am ET to 1:08am ET)? We saw them the first time during the time you posted in your original post.
06-15-2021 06:03 AM
Since the update (2021-06-11) to malware this has caused significant malware alerts. To my knowledge there hasn't been any help desk tickets that parts of the internet isn't working.... Has anyone reached out to #Unit42 for an explanation?
06-15-2021 07:35 AM - edited 06-15-2021 07:56 AM
Yeah we got bombarded by a few thousand all at once in that timeframe, I have them set to ignore until I see any evidence to suggest that they're something I should actually be concerned about.
06-15-2021 08:01 AM
We didn't see thousands but this happened on 6/11 (matching the time frame from the OP), and then last night between between 12:33am and 1:08am ET. We ran full Bitdefender and Malwarebytes scan, both came back clean. Hoping this is just a categorization failure on the Palo Threat detections but seems odd it happened twice in 4 days.
06-15-2021 08:04 AM - edited 06-15-2021 08:11 AM
I think I see what happened; a bunch of new detections for malware communicating with that letsencrypt domain are now visible in VirusTotal, when they weren't last night. WildFire probably got that data earlier than it was available publicly on VirusTotal. The Let'sEncrypt domain likely isn't malicious, but some malware is pointing to it for some reason (maybe to check validity on a cert? sounds like it might be a cheeky way to do CNC signalling using a public service). That doesn't explain why it has happened twice in 4 days though. Maybe some other data source reported it 4 days ago and they disabled the signature once they realized it wasn't an actionable alert, then re-enabled it when more detections popped up through VT?
06-15-2021 09:14 AM
Certainly possible. I am concerned if your theory is true. That would indicate several endpoints have some undetected malware on them. We fortunately block traffic to this specific endpoint, although only when categorized as malware. Otherwise I see traffic to this endpoint going back weeks. We are opening a case with Palo TAC support to better understand what is going on. If we identify root cause I will provide an update here.
06-15-2021 09:45 AM
We have been seeing a spike in alerts for this as well. Logs shows connections to the IPs going back to at least 6/8. Internally, it looks like the DNS requests are being generated from hmpalert.dll on a large number of machines, which is apparently the HitmanPro.Alert service, part of Sophos. We are still investigating.
06-15-2021 11:34 AM
I'd be interested to know the root cause if you figure it out.
06-15-2021 01:08 PM
This is a false positive. Palo Alto support provided the following:
I understand you are looking for a reason why this URL was marked as malware and why it flipped back. This domain is not malware, it was accidentally released last night, and as soon as we realized it was flip to shareware and disabled it. We are in the process of taking steps, such as adding this and some subdomains under lencr.org found in our database in a restrictive white list, domains under that list can't be released to malware. That step will avoid the similar FP case is caused in future.
06-15-2021 02:09 PM
Thanks for letting me know.
06-15-2021 04:20 PM
This signature is been disabled, and this domain( including some of the sub-domain) are categorized as Computer and Internet Info, Low Risk.
let me know if you have any more question
06-25-2021 08:04 AM
We are still seeing this domain show up as a confidence of 4 for botnet. Is anyone seeing the same? (or should I post this as a new discussion?)
Repeatedly visited (12) the same malicious URL x1.c.lencr.org/
06-25-2021 08:49 AM - edited 06-25-2021 08:51 AM
Showing up as a PA threat for the DNS query or for the URL on a block list? The original thread was for a DNS lookup threat of supposed malware. In our logs we were getting DNS threat hits and blocks from approximately 6/11 16:30 GMT until 6/15 7:45 GMT. We have not had any threat alerts since, though we continue to see intermittent traffic to the destination.
The x1.c.lencr.org DNS/URL is not a threat itself (that I have been able to find). It is a valid Lets Encrypt domain and returns a certificate revocation list when queried. In our case we tracked it down to a component of Sophos making the queries (doing HTTP GET for the root doc with a modifier: if changed since Sep 4 2020, it hasn't been so a 304 Not Modified was returned). It appears that suspected malware may have also been querying the URL (probably for a Lets Encrypt cert generated for the malware) and the entire domain was erroneously included as a threat.
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