Re: Creating a rule for RDP

[Johnathan Wiltberger <johwiltb () gmail com>]

If someone wanted to, though, could you look at the response size coming
back?

As in, a failed login for RDP is A bytes, a successful login is B bytes (or
maybe just ~A), then if you see your server response be A bytes 3 times,
then trigger a block on the source IP.  Not the best technique maybe, but
it was one of the ways I would try to detect failed SSH logins a while ago.

John Wiltberger

On Sat, Feb 7, 2015 at 3:06 AM, Samuel M Westerfeld <sam () utexas edu> wrote:

> No need to reinvent the wheel. This can (and should) be done through Group
> Policy or Local Security Policy in Windows.
> On Feb 7, 2015 1:36 AM, "Dave Killion" <dave.killion () gmail com> wrote:
>
> > While that's true - RDP is encrypted - a poor man's brute-force detection
> > is to detect n-connections in y seconds between IP peers.  Say... 5
> > connections in 10 seconds?
> >
> > A real user wouldn't go that fast unless they were rapidly trying
> > credentials, and a script would go much faster.   You may need to tune the
> > interval, however, to something that makes sense in your network.
> >
> > Yes, this has problems with NAT, and yes, it has problems with slow
> > brute, but... It's better than nothing, and I know with certainty that many
> > commercial IDS' do exactly this.
> >
> > Dave Killion
> >
> >
> > > On Feb 6, 2015, at 4:57 PM, Jason Haar <Jason_Haar () trimble com> wrote:
> > >
> > > > On 23/01/15 12:06, Richard Giles wrote:
> > > > Hello,
> > > >
> > > > I am trying to write a simple snort rule that will block RDP traffic
> > if the password is failed more then 3-5 times. I have been experimenting
> > using something like the following:
> > > >
> > > As far as I'm aware RDP is a fully encrypted channel, so any failed
> > login messages are sent by the server to the client over that encrypted
> > channel. In other words, it's just like SSH
> > > ie snort can't read it.
> > >
> > > The only way I can think of to detect RDP failed logins is to monitor
> > the eventlogs of Windows servers for failed login events :-(
> > > --
> > > Cheers
> > >
> > > Jason Haar
> > > Corporate Information Security Manager, Trimble Navigation Ltd.
> > > Phone: +1 408 481 8171
> > > PGP Fingerprint: 7A2E 0407 C9A6 CAF6 2B9F 8422 C063 5EBB FE1D 66D1
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look and join the conversation now. http://goparallel.sourceforge.net/

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