TCP Dup ACK on port 3389

Hi

On a Windows SBS 2008 R2 I am running Wireshark to understand what might be causing slow network file transfers with the server.

I have consequently noticed numerous TCP Dup ACK lines and some coming from outside the network e.g. Kuwait, Gabon, Deutschland, ...

What is curious is that these TCP Dup ACK packets are all aimed at port 3389 (Terminal Server). Therefore I can assume that someone(s) is trying to get 'in'.

Is there such a thing as a Dup ACK ddos attack?

Not sure what to do to discourage these attempts

If I had a Mikrotik router at this client's site I could add these entries into an Address list, drop further attempts, and forget about them.

Can I do anything similar under W2K8 SBS R2 ?

thanks
yann
Yann ShukorOwnerAsked:
Who is Participating?

[Product update] Infrastructure Analysis Tool is now available with Business Accounts.Learn More

x
I wear a lot of hats...

"The solutions and answers provided on Experts Exchange have been extremely helpful to me over the last few years. I wear a lot of hats - Developer, Database Administrator, Help Desk, etc., so I know a lot of things but not a lot about one thing. Experts Exchange gives me answers from people who do know a lot about one thing, in a easy to use platform." -Todd S.

JAN PAKULAICT Infranstructure ManagerCommented:
Had similar problem - your RDP  is being brute forced:)

several options here

1 disable 3389
2 use rdp though https gateway (rdweb)
3 Or like me get yourself that http://rdpguard.com/  (use ip block - it will block access after set amount of wrong password)
( just to clarify - i am not employee of this company :-))
0

Experts Exchange Solution brought to you by

Your issues matter to us.

Facing a tech roadblock? Get the help and guidance you need from experienced professionals who care. Ask your question anytime, anywhere, with no hassle.

Start your 7-day free trial
Dan CraciunIT ConsultantCommented:
Or, if you only RDP from a known list of IPs, add those as a rule in Windows Firewall.

I always considered whitelisting safer than blacklisting...

HTH,
Dan
0
It's more than this solution.Get answers and train to solve all your tech problems - anytime, anywhere.Try it for free Edge Out The Competitionfor your dream job with proven skills and certifications.Get started today Stand Outas the employee with proven skills.Start learning today for free Move Your Career Forwardwith certification training in the latest technologies.Start your trial today
Windows Server 2008

From novice to tech pro — start learning today.