Threat Level: green Handler on Duty: Didier Stevens

SANS ISC: Your Bill Is Not Overdue today! - Internet Security | DShield SANS ISC InfoSec Forums


Sign Up for Free!   Forgot Password?
Log In or Sign Up for Free!
Your Bill Is Not Overdue today!

Just as little as yesterday's order that "proceeded."  It Look like today's ransomware subject is "Your Bill is Overdue." But then again, don't bother blocking it. Block ZIP'ed visual basic scripts. This round of Locky makes blocking a tad harder by using "application/octet-stream" as a Content-Type instead of "application/zip."

(and about 2 hrs after publishing this diary, another small update: the Content-Type now changed to application/x-compressed . Makes you wonder if they are reading this ;-) )

It may be safe to strip everything with an "application/octet-stream" attachment. 

For the last 30 minutes, I received just about 1,000 attachments like that, and about 4000 total. The first one I received arrived just after 8 am UTC.

Anti-Virus coverage is spotty as usual. Kaspersky and Sophos seem to be doing a rather good job lately detecting the initial downloaders

As usual, Xavier's mime-zip-trojan script does a beautiful job of keeping these attachments out of your inbox:

https://github.com/xme/toolbox/blob/master/mime-zip-trojan.pl

 

 

---
Johannes B. Ullrich, Ph.D.
STI|Twitter|LinkedIn

I will be teaching next: Defending Web Applications Security Essentials - SANS Brussels September 2019

Johannes

3608 Posts
ISC Handler
We received a batch of "credit card charge from [ourdomain]" emails; from "angry customer"; "what is this f charge on my card?" .. "I want my money back!!!"..

The attached file was titled "statement_[ourdomain]_#####.doc" (5 digits)

dotBATman
dotBATman

63 Posts
Please wake me up when consensus has been reached that domain whitelisting is required to have any hope in stopping this madness.

btw,
I have a open source / free App that will make domain whitelisting management a lot easier for the IT dept and might help educate users as well.

This is how it works
-set workstation dns server to 127.0.0.1
-configure App to point to your corporate DNS server
-configure App to trust Alexa top 10,000 domains or more if you want.
-Note App uses dnsjack.js, 287 beautiful lines of javascript written by @mafintosh.
-App will NOT bypass your DNS server. Anything blocked on DNS server will be blocked for the user.
-If a user clicks on a phishing link, the user will have to approve the domain, and click the link again.

https://pbs.twimg.com/media/CvkM3vVWgAAm_uv.jpg
https://pbs.twimg.com/media/CvkM5ZrWgAAD9Ui.jpg

Please DM me on twitter if you want more info.
@mabraFoo
Washington D.C.
mabraFoo

9 Posts
@mabraFoo

Domain whitelisting may help some but it's not really a complete solution. PLENTY of maliciousness can potentially come from domains you will whitelist / the Alexa top whatever. Not saying it won't cut the noise considerably but realistically if the user clicked the link they'll click the approve button too because they didn't open the page by accident. Their logic is "I clicked this of course I want to go here. I get this dumb page any time I'm trying to do anything on the web." It will become automatic. You will be mocked and resented by your users just like Vista users did Microsoft when all the UAC popups started happening.
Anonymous
Anonymous, you are correct, it is not a complete solution. However, one thing that is very important and really hard to block are new domains (see github.com/hasameli/foghorn).

Another advantage that an App like this could help with is auditing DNS events. Also, I don't know of a way to easily configure DNS to be strict for some departments and more open for other departments in a company.

Mick Douglas knows a lot more than I do about preventing malware / ransomware. I recommend everyone watch his Derbycon talk. Great stuff!
https://www.youtube.com/watch?v=4MdMSoTiqDM
mabraFoo

9 Posts
This new functionality in the DNS server of Windows Server 2016 should be worth looking into:

technet.microsoft.com/en-us/windows-server-docs/networking/dns/what-s-new-in-dns-server

New functionality: DNS Policies
You can configure DNS policies to specify how a DNS server responds to DNS queries. DNS responses can be based on client IP address (location), time of the day, and several other parameters. DNS policies enable location-aware DNS, traffic management, load balancing, split-brain DNS, and other scenarios.
dotBATman

63 Posts

Sign Up for Free or Log In to start participating in the conversation!