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Event ID 529 in the Thousands

msiers
msiers asked
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Last Modified: 2012-08-13
A few of our clients get between 50-100 event 529s per day in Security Event Log. Lately with two of our clients, we are seeing them in the THOUSANDS, from foreign IP addresses. I usually document the IP as best I can via ip-lookup.net and try to get a region identifier. Many times the IP ranges aren't registered with ARIN. Also, we see these coming from various regions on a day-to-day basis: Sometimes from Germany, Spain, Russia, US, Australia, etc.

Is there a standard best-practice in auditing these events and is there a solution such as changing RDP ports or some such we should look into? Does everyone see these events often, or is this possibly something we've overlooked? Thanks!
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Commented:
When you say "clients," are you referring to people/companies or computers?

In either case, why are you permitting RDP access to internal machines from the Internet directly?  I would setup a Terminal Services Gateway.

Worst case, change the port RDP responds to either locally on each machine of via a NAT/PAT on your firewall (you do have one, right?). :-)

Commented:
Best thing would be to setup a VPN then connect via RDP after connecting to the VPN.

If you setup a TSGateway, put the TSGateway in your DMZ and only allow required traffic to/from it and your internal network and also to/from it and the Internet.
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Commented:
http://www.ip-adress.com/whois/222.186.23.74

Well another issue we have is that our clients are small businesses. None of our clients are related or have much in common with one-another, and nothing obvious about who our clients are. It's really strange to see this above IP hit two of my clients in the same day. Very strange, rare, and seemingly almost impossible.

[***] = Proprietary information
_________________________
Logon Failure:
Reason: Unknown user name or bad password
User Name: Administrator
Domain: [client's domain]
Logon Type: 10
Logon Process: User32
Authentication Package: Negotiate Workstation
Name: [servername]
Caller User Name: [servername]$
Caller Domain: [client's domain]
Caller Logon ID: (0x0,0x3E7)
Caller Process ID: 6892
Transited Services: -
Source Network Address: 222.186.23.74
Source Port: 1720

I am new to this aspect of administration, so pardon my lack of knowledge in the best practices on researching this sort of event and preventing it down the road. This IP/entity shouldn't have any ability to identify two of our customers and hit them the same day, it just seems highly improbable.

Author

Commented:
Oh, and pretty much every client gets these from external IPs, usually the same Logon and Process type and ID.
btanExec Consultant
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Commented:
Looks like it is indeed some brute forcing remote attempts but failed.
Can see this check of IP in robtex
@ http://www.robtex.com/ip/222.186.23.74.html

It is within the past blacklist and I will suggest that the ip be blackholed at your firewall or network defence devices. Keep all machine up to latest patch too.
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