SMTP Strangeness - Possible C2
We received an email today that provided some interesting information from a reader (Bjorn) about some observed SMTP traffic that was unusal. From the appearance it could be related to exfil or C2. The domain in question is donotspamtoday.com whose IP is 185.14.30.147 and there is an DNS TXT entry for SPF. The domain was registered March 20, 2018. I have been unable to find any additional examples or information of similar traffic.
Bjorn provided a good analysis of what was observed and I'd like to pass it along to see if anyone is seeing or has seen traffic similar to this. Here is what he sent to us:
multiple compromised mail accounts being abused for some kind of covert channel communication. These are the common denominators in the mail communication:
* Mail is submitted to the domain donotspamtoday.com, with a lowercase first name and single digit as local part of the address (kevin1@, joan4@, willy3@ etc)
* When sending mail, the client identifies with a HELO name of 10 random lowercase characters (helo=<ckvcjsgffo>, helo=<uhtcpnyawr>, helo=<mjjrdvztxq> etc)
* The mail's Subject is always three (3) garbled/hashed words, followed by MID: and 32 hex characters. Some examples:
Subject: tjx gxtew kfzmmi MID:
Subject: yjlp tahfhg bhj MID:
Subject: oezdvlh nbqhhd smbhmh MID:
Subject: kiyeax ggsqfeb aucilpi MID:
Subject: tqorgfj crngne jwkbljt MID:
Subject: jhwz nchfa ujk MID:
Subject: obem jzmep nju MID:
Subject: zqfn gkdepn vjyuu MID:
Subject: ghod ttfq dqge MID:
* Each mail body contains exactly one line of eight hashed words. The words in the mail body are different from the words in the subject. Some examples (one line from each mail):
zjmviov rdktiw ovzdebu ysm htp kzhfsk escngpg oqcru
nklnhk lidwen qeujgbe lcrz krf xufkyb xqpjqbg nto
gcbvqzq dca wlfig prgrkg hmbzjn yxl uov lxwak
cxkw jnv vezxdkz sfvib rqnyze fqkfwgs memck cwm
* Most clients sending the mails connect from Brazil, but some connect from Iran, Turkey and others. The IPs observed exposing this behaviour are registered with Open Threat Exchange, https://otx.alienvault.com/
If anyone has any additional information or is seeing this traffic, please let us know.
Lorna Hutcheson
ISC Handler
Comments
Anonymous
Dec 3rd 2022
10 months ago
Anonymous
Dec 3rd 2022
10 months ago
<a hreaf="https://technolytical.com/">the social network</a> is described as follows because they respect your privacy and keep your data secure. The social networks are not interested in collecting data about you. They don't care about what you're doing, or what you like. They don't want to know who you talk to, or where you go.
<a hreaf="https://technolytical.com/">the social network</a> is not interested in collecting data about you. They don't care about what you're doing, or what you like. They don't want to know who you talk to, or where you go. The social networks only collect the minimum amount of information required for the service that they provide. Your personal information is kept private, and is never shared with other companies without your permission
Anonymous
Dec 26th 2022
9 months ago
Anonymous
Dec 26th 2022
9 months ago
<a hreaf="https://defineprogramming.com/the-public-bathroom-near-me-find-nearest-public-toilet/"> nearest public toilet to me</a>
<a hreaf="https://defineprogramming.com/the-public-bathroom-near-me-find-nearest-public-toilet/"> public bathroom near me</a>
Anonymous
Dec 26th 2022
9 months ago
<a hreaf="https://defineprogramming.com/the-public-bathroom-near-me-find-nearest-public-toilet/"> nearest public toilet to me</a>
<a hreaf="https://defineprogramming.com/the-public-bathroom-near-me-find-nearest-public-toilet/"> public bathroom near me</a>
Anonymous
Dec 26th 2022
9 months ago
Anonymous
Dec 26th 2022
9 months ago
https://defineprogramming.com/
Dec 26th 2022
9 months ago
distribute malware. Even if the URL listed on the ad shows a legitimate website, subsequent ad traffic can easily lead to a fake page. Different types of malware are distributed in this manner. I've seen IcedID (Bokbot), Gozi/ISFB, and various information stealers distributed through fake software websites that were provided through Google ad traffic. I submitted malicious files from this example to VirusTotal and found a low rate of detection, with some files not showing as malware at all. Additionally, domains associated with this infection frequently change. That might make it hard to detect.
https://clickercounter.org/
https://defineprogramming.com/
Dec 26th 2022
9 months ago
rthrth
Jan 2nd 2023
9 months ago