Mitigate Ransomware "WannaCry"

BBcan177

http://blog.talosintelligence.com/2017/05/wannacry.html

Additionally, organizations should strongly consider blocking connections to TOR nodes and TOR traffic on network. Known TOR exit nodes are listed within the Security Intelligence feed of ASA Firepower devices. Enabling this to be blacklisted will prevent outbound communications to TOR networks.

jimp

You should also create DNS Resolver or DNS Forwarder host overrides to point the following domain names at a LIVE HTTP server on your local network (NOT at the firewall!)


ifferfsodp9ifjaposdfjhgosurijfaewrwergwea.com
iuqerfsodp9ifjaposdfjhgosurijfaewrwergwea.com
iuqssfsodp9ifjaposdfjhgosurijfaewrwergwea.com
iuqerfsodp9ifjaposdfjhgosurijfaewrwergwea.com
ayylmaotjhsstasdfasdfasdfasdfasdfasdfasdf.com

These are killswitch domains and if the malware can access these domains, it stops propagating. It does not require any specific response, only that it can make an HTTP request to those domains. The domains have been sinkholed already but on the outside chance there is a DoS against those you don't want to rely on the public servers being available.

DO NOT BLOCK THESE DOMAINS, blocking solves nothing. It is not a C&C server, but a killswitch.

EDIT: Added new killswitch domains

athurdent

@BBcan177:

http://blog.talosintelligence.com/2017/05/wannacry.html

Additionally, organizations should strongly consider blocking connections to TOR nodes and TOR traffic on network. Known TOR exit nodes are listed within the Security Intelligence feed of ASA Firepower devices. Enabling this to be blacklisted will prevent outbound communications to TOR networks.

Hmm, strange IP notation there, what could this mean? Some kind of regexp?

188[.]166[.]23[.]127:443 - Tor Exit Node
213.61.66[.]116 - Tor Exit Node

jimp

@athurdent:

Hmm, strange IP notation there, what could this mean? Some kind of regexp?
188[.]166[.]23[.]127:443 - Tor Exit Node
213.61.66[.]116 - Tor Exit Node

More likely they are trying to make it NOT create a link when copy/pasted, so (a) people don't click links to potentially malicious content and (b) so people don't easily spread those links by copy/pasting content from the source.

athurdent

Great thanks!

BBcan177

@jimp:

You should also create DNS Resolver or DNS Forwarder host overrides to point the following domain names at a LIVE HTTP server on your local network (NOT at the firewall!)
ifferfsodp9ifjaposdfjhgosurijfaewrwergwea.com
iuqerfsodp9ifjaposdfjhgosurijfaewrwergwea.com
iuqssfsodp9ifjaposdfjhgosurijfaewrwergwea.com
iuqerfsodp9ifjaposdfjhgosurijfaewrwergwea.com
ayylmaotjhsstasdfasdfasdfasdfasdfasdfasdf.com
These are killswitch domains and if the malware can access these domains, it stops propagating. It does not require any specific response, only that it can make an HTTP request to those domains. The domains have been sinkholed already but on the outside chance there is a DoS against those you don't want to rely on the public servers being available.

DO NOT BLOCK THESE DOMAINS, blocking solves nothing. It is not a C&C server, but a killswitch.

EDIT: Added new killswitch domains

Keep in mind that this would override just that domain and not "www."
Would need to create two forwards for each domain to be safe. Hopefully everyone has patched their software as recommended…

GruensFroeschli

Keep in mind that this killswitch is only valid for earlier version(s) of Wcry.
At least one currently circulating version doesn't have this killswitch anymore.

johnpoz

"At least one currently circulating version doesn't have this killswitch anymore."

That they would include a killswitch in the first place seems odd.. Why would I want to kill something that is meant to make me money ;)

GruensFroeschli

Was wondering the same ^^"

I could imagine that quite some parts of it are copy/paste code…

jimp

If they deployed it but they found that it wasn't working like they wanted, they could stop it and make changes before it spread too far and reduced their chances of a bigger payout by going undetected for a longer period. So a kill switch makes sense, but they didn't bother to actually register their killswitch domains, so…

NOYB

@jimp:

If they deployed it but they found that it wasn't working like they wanted, they could stop it and make changes before it spread too far and reduced their chances of a bigger payout by going undetected for a longer period. So a kill switch makes sense, but they didn't bother to actually register their killswitch domains, so…

I was thinking it was their way of preventing a boomerang affect on them and their cohorts. In which case there would be no need to register the domains. Just make them available in environments they don't want affected.

johnpoz

"Just make them available in environments they don't want affected."

Wouldn't you just make sure places you don't want to be affected are updated against whatever exploit your using. I guess if you were using an exploit that was not patched ;) having a way to kill it would be good. And Jimp makes a good point as well.

Both very viable answers to reason for killswitch - thanks.

NOYB

@johnpoz:

"Just make them available in environments they don't want affected."

Wouldn't you just make sure places you don't want to be affected are updated against whatever exploit your using. I guess if you were using an exploit that was not patched ;) having a way to kill it would be good. And Jimp makes a good point as well.

Both very viable answers to reason for killswitch - thanks.

In addition to perhaps a not yet patched exploit. Perhaps the environments not to be affected are vast and not under direct control for patching. A domain/web site based kill switch could also be used for targeting attack (exclude non targeted environments). For instance nation states and cyber warfare.

Though it could also be just as simple as an oversight to remove test/debug/example code.

jimp

They could also sell the killswitch to some places for more $$$

NOYB

@jimp:

They could also sell the killswitch to some places for more $$$

Yup, lots of possibilities.

What made me think of cyber warfare was a top 20 chart I saw with one particular nation affected way more than any other. Another thought on cyber warfare could be nation C trying to stoke animosity between nations A and B.

General public pawns will probably never know much of any of this. But it is fun to speculate.

Hmmm. They would only be able to sell the kill switch once. Then everyone would have it. Also, why two kill switches? Seems to me that may indicate targeting.

NOYB

The simple reason so many companies were hit by the WannaCry 2.0 ransomware

Daniel Howley
Technology Editor

Yahoo FinanceMay 16, 2017

https://finance.yahoo.com/news/simple-reason-many-companies-hit-wannacry-2-0-ransomware-192836300.html

Excuses, excuses. It's their job/responsibility to operate a secure environment. If they are unable or unwilling to allocate the necessary resources to accomplish that then it is their fault, and stupidity for taking the associated risk without being prepared to deal with the possible consequences.

zoro_2009

<interrup>Whats a killswitch ?</interrup>

jimp

@zoro_2009:

<interrup>Whats a killswitch ?</interrup>

It's a condition that, if met, causes a program to stop executing.

In this case, the malware checks to see if one of the domains is live (attempts an HTTP connection to it). If this succeeds, then it does not attempt to spread itself further.

So by making sure the malware can access these "killswitch" domains, you effectively stop it from infecting more machines, giving you more time to get your systems patched/configured/etc to properly prevent them from being exploited, and to clean up existing infections.

fredfox_uk

For a really good explanation of the killswitch take a read of this https://www.malwaretech.com/2017/05/how-to-accidentally-stop-a-global-cyber-attacks.html

zoro_2009

thanks