Possible Fake-AV Ads from Doubleclick Servers
Reader James ran into a Fake AV ad delivered by Double click. It is not clear if this is the result of a compromise of double click, or a paid ad that slipped through doubleclick's content review process. James' started out at a local new paper web site, that like many others features ads served by double click. Luckily, James used a proxy tool (Fiddler) to record the session. Here are some of the excerpts (slightly anonymized and spaces inserted to avoid accidental clicks):
GET http://ad.doubleclick.net/adj/mi.ida00/News;atf=n;dcove=d;pl=sectfront;sect=News;
pos=2;sz=300x250;tile=8;!c=news;gender=;year=;income=;ord=230528779772346? HTTP/1.1
Accept: */*
Referer: [local newspaper URL]
Accept-Language: en-us
User-Agent: Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.1; Trident/4.0; [...]
Accept-Encoding: gzip, deflate
Host: ad.doubleclick.net
Connection: Keep-Alive
Cookie: id=xxxxa||t=1352150000|et=730|cs=yyyy
The reply to this request was:
HTTP/1.1 200 OK
Content-Type: application/x-javascript
Content-Length: 167
Date: Mon, 05 Nov 2012 22:32:59 GMT
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Johannes B. Ullrich, Ph.D.
SANS Technology Institute
Twitter
Reminder: Ongoing SMTP Brute Forcing Attacks
Our reader (and podcast listener) Pete wrote in with a little SMTP log snippet:
2012-11-04 22:37:36 courier_login authenticator failed for 153.red-2-139-216.staticip.rima-tde.net ([192.168.2.33]) [2.139.216.153]:4232: 535 Incorrect authentication data (set_id=anna)
2012-11-04 22:37:36 courier_login authenticator failed for 153.red-2-139-216.staticip.rima-tde.net ([192.168.2.33]) [2.139.216.153]:4232: 535 Incorrect authentication data (set_id=anna)
2012-11-04 22:37:37 courier_login authenticator failed for 153.red-2-139-216.staticip.rima-tde.net ([192.168.2.33]) [2.139.216.153]:4232: 535 Incorrect authentication data (set_id=anna)
2012-11-04 22:37:37 courier_login authenticator failed for 153.red-2-139-216.staticip.rima-tde.net ([192.168.2.33]) [2.139.216.153]:4232: 535 Incorrect authentication data (set_id=anna)
2012-11-04 22:37:38 courier_login authenticator failed for 153.red-2-139-216.staticip.rima-tde.net ([192.168.2.33]) [2.139.216.153]:4232: 535 Incorrect authentication data (set_id=anna)
In this case, the attacker is '2.139.216.153'. According to our DShield data, the host has a history of port 25 scanning, and evidently, participates in these brute force attacks once it finds port 25 open. (see https://isc.sans.edu/ipdetails.html?ip=2.139.216.153 ).
But this is just one of many IPs that Pete sees coming into his network. They all use "192.168.2.33" as hostname, which appears to be hard coded into the bot used to produce these scans.
Typically, these scans try to brute force SMTP credentials (not POP/IMAP credentials) to send spam via your users e-mail accounts. A few tips to help mitigate these attacks:
- enable rate limits for inbound authentication attempts. This will at least slow down the attack. (consult your mail servers manual for details. Each server is different)
- enable reasonable rate limits for outbound email. This way, it is easier to detect compromised accounts, and the account is of less value to the spammer
- do not rely on passwords. Use SSL client certificates (or at least enforce a strong password policy)
- only allow connections to send mail from inside your network, or via a VPN.
Any other ideas? FWIW: I do not recommend strict "lock out" policies for mail servers. They can make it impossible to change your SMTP password. Many users will use multiple devices these days, and if you for example lock an account after 3 bad logins, a user changing a password will be locked out as the users cell phone / tablet will continue to use the old password until it is changed. If you do implement lock out, then please communicate this to your users and ask them to first turn off all devices (that can be challenging as they may not even remember which devices they have) and then change their password.
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Johannes B. Ullrich, Ph.D.
SANS Technology Institute
Twitter
Comments
Anonymous
Dec 3rd 2022
9 months ago
Anonymous
Dec 3rd 2022
9 months ago
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Anonymous
Dec 26th 2022
9 months ago
Anonymous
Dec 26th 2022
9 months ago
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Anonymous
Dec 26th 2022
9 months ago
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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
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Jan 2nd 2023
8 months ago