Analysis of a large brute force attack campaign against Windows Remote Desktop

71 pointsby rmdossalmost 3 years ago

11 comments

LinuxBenderalmost 3 years ago

They do not appear to be ramping up on any of my VPS nodes. I see the same averages to my tarpit ports on all my nodes.<pre><code> # VPS They all look similar to this iptables -L INPUT -n -v | grep TAR | sort -r | awk '{print $1"\t" $3"\t" $11}' 2680 TARPIT dpt:23 2657 TARPIT dpt:6379 170K TARPIT dpt:445 1186 TARPIT dpt:80 882 TARPIT dpt:22 757 TARPIT dpt:443 591 TARPIT dpt:5900 311 TARPIT dpt:21 296 TARPIT dpt:3389 119 TARPIT dpt:873 </code></pre> Some poorly coded bots appear to get stuck on 445 indefinitely. On the other hand I do see a vast increase on my home network to 5900 VNC. It is usually about double the hits to 3389 RDP<pre><code> # Home iptables -L INPUT -n -v | grep TAR | sort -r | awk '{print $1"\t" $3"\t" $11}' 9013 TARPIT dpt:5900 1628 TARPIT dpt:22 1274 TARPIT dpt:23 1092 TARPIT dpt:445 119 TARPIT dpt:3389 40 TARPIT dpt:21 </code></pre> [Edit] Here is a second home connection that has a higher uptime. Running tcpdump it looks like the latest VNC bots do not recognize and avoid tarpits.<pre><code> # Second Home connection iptables -L INPUT -n -v | grep TAR | sort -r | awk '{print $1"\t" $3"\t" $11}' 50532 TARPIT dpt:22 44301 TARPIT dpt:445 33520 TARPIT dpt:23 6718 TARPIT dpt:80 6439 TARPIT dpt:3389 184K TARPIT dpt:5900 1091 TARPIT dpt:21 271 TARPIT dpt:1900</code></pre>

dontbenebbyalmost 3 years ago

Why don't more people use Fail2Ban?<a href="https://www.fail2ban.org/wiki/index.php/Main_Page" rel="nofollow">https://www.fail2ban.org/wiki/index.php/Main_Page</a>I avoided running servers since people are jerks but if I did that would be on my checklist of things to set up if I intended one to stick around long term.People seem to reinvent concepts from long ago for reasons I do not understand.

评论 #31632212 未加载

评论 #31632588 未加载

technionalmost 3 years ago

As someone who supports a lot of Windows environments - yes, it's incredible the rate at which this occurs. I'd strongly point people at the RD Gateway MFA plugin as a requisite for publishing RDS these days:<a href="https://docs.microsoft.com/en-us/azure/active-directory/authentication/howto-mfa-nps-extension-rdg" rel="nofollow">https://docs.microsoft.com/en-us/azure/active-directory/auth...</a>It's also supported to publish behind the Azure App Proxy, avoiding the need for any port forwards at all:<a href="https://docs.microsoft.com/en-us/azure/active-directory/app-proxy/application-proxy-integrate-with-remote-desktop-services" rel="nofollow">https://docs.microsoft.com/en-us/azure/active-directory/app-...</a>

评论 #31629651 未加载

评论 #31629959 未加载

frogger8almost 3 years ago

<a href="https://github.com/devnulli/EvlWatcher" rel="nofollow">https://github.com/devnulli/EvlWatcher</a>README…It's basically a fail2ban for windows. Its goals are also mainly what we love about fail2ban:pre-configured no-initial-ducking-around-with-scripts-or-config-files install-and-forget You can download it here ( v2.1.5 - April 2022 ) .Also, we love issues!If anyone needs something or has questions about something, please feel free to open an issue. We are especially happy to get issues about log-entry samples we don't react on, or ideas of how we can support more protocols.A bit more detailed description of what EvlWatcher does.Scenario: there are those bad people out there, hammering your service (RDP and whatnot) with brute force attempts.You can see them and their IPs clearly in the Windows Event-Log.You have searched the web and yea, there are plenty of tools, scripts, and all that, to read the event-log and automatically ban the attackers IP.You however, are lazy. You need something like fail2ban, with a preconfigured set of rules to just RUN right away and it works.But then, it still needs enough flexibility for you to completely configure it, should you wish to do so. EvlWatcher does that. It scans the Windows-Event-Log, and reacts.It works by installing a service that scans the event log for unsuccessful login attempts. When one of its rules are violated (e.g. trying to log in without correct credentials, more than 5 times in 2 minutes), it will place that poor bastard into a generic firewall rule, and thereby ban the attacker for 2 hours.Also, when someone is repeatedly trying, there is a permanent ban list for that, where people defaultly land on when they've had three strikes.You can, of course, adjust the rules to your liking. They are basically a consisting of an event source, and a Regex to extract an IP, its pretty simple.

评论 #31630995 未加载

ozimalmost 3 years ago

Well I never ever expose RDP to the internet directly. Allow only office IP or setup some VPN/jumphost via ssh whatever.I trust SSH much more than RDP to not have RCE/auth bypass bugs. SSH is also much easier to setup key auth or 2FA than in RDP if one like they mentioned in post are more used to setting up Linux boxes.After reading this blog post - I would not send any logs to their servers.

评论 #31632103 未加载

评论 #31632063 未加载

gambitingalmost 3 years ago

Yep, I have a single Windows Server machine with an RDP port(non default) exposed to the world and it gets tens of thousands of failed logins every day. It has been for the past few years. I have no idea who is wasting their time on this or why, but as far as I can tell it's costing me nothing, so other than setting up an alert for a successful login I decided to simply ignore it.

TazeTSchnitzelalmost 3 years ago

The difference between type 3 and type 10 is probably the difference between providing the username and password when connecting to RDP or after already connecting. In the latter case it's “interactive”: you enter the password via the GUI of the server you connected to.

tg180almost 3 years ago

I had to ban Flyservers on many occasions too.Given the frequency with which these incidents happen, I am more inclined to think they are a bulletproof hoster of some kind ...At a certain point it becomes difficult to attribute things to “incompetence” rather than malicious intent

Neil44almost 3 years ago

There’s a pretty cheap program that will do auto blocking, it’s easily googleable. Also changing the default port will cut down the numbers. I’ve had one hacked over RD gateway so that alone isn’t the answer. On our cloud windows servers we use a remote management agent to access, this obvs has its own trust issues but overall works well.

300bpsalmost 3 years ago

Windows do not log the passwords they tried, so we can't know which ones were usedWould be interesting to create a server daemon that listens on TCP port 3389 and implements the login portion of the RDP protocol to 1) Be able to gather information about the passwords used and 2) Experiment with ways to lock up or stall the scanners.

评论 #31632307 未加载

johnklosalmost 3 years ago

You absolutely should blame Flyserver. They allow bots to run, and they don't do anything about it. There are too many network operators like this.Imagine if any networks where constant and ongoing illegal activity happens, and the network operators do nothing, eventually result in those networks being taken away. Things would change drastically.