Solved

Somebody sent spam using one of my users accounts

Posted on 2008-06-24
2
217 Views
Last Modified: 2010-04-21
I have a simple one domain, one exchange server (2003) system.  One of my 70 users came in the other day to find 500 undeliverable messages in her Outlook.  They were all spam using her account.I checked MXLOOKUP and we do not have an open relay.  There are only a few messages in my System Manager queue.  This is a one-time occurrence.  Should I ignore it and see if it repeats?  Or what should I check to prevent a reoccurrence.  Our incoming mail goes through a spam filter, but I don't believe our outgoing mail does.
0
Comment
Question by:tomcurrier
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
2 Comments
 
LVL 71

Accepted Solution

by:
Chris Dent earned 500 total points
ID: 21863821

Not an uncommon situation unfortunately.

It's likely that the spam didn't originate at your servers at all. Spoofing SMTP addresses is utterly trivial so pretty much anyone can pick up an address and use it as they wish.

You don't get a great deal of choice about what you do with this. Your only option to help reduce the impact should it occur again is to add an SPF (Sender Policy Framework) record for your domain (a TXT Record on your public DNS Server).

The SPF Record allows you to explicitly declare which IP addresses are permitted to send mail for your domain name. It's an extremely useful mechanism for reducing abuse as you've seen above.

The tricky bit is that it is impossible to completely stop abuse like this, SMTP is inherently insecure. Things like SPF sit on top of (or in front of) SMTP and attempt to add a level of security. Not everyone checks SPF Records though. Those that don't will still return NDRs without further consideration. And not all ISPs allow you to add them, an annoying situation.

For instructions (and wizards) for generating SPF Records you can use either this site (this one also contains full details of the syntax):

http://www.openspf.org/

Or this one:

http://www.microsoft.com/mscorp/safety/content/technologies/senderid/wizard/

If you've created yourself a record and aren't sure at all please don't hesitate to post back.

HTH

Chris
0
 

Author Closing Comment

by:tomcurrier
ID: 31470365
Chris, many thanks.  That helps
0

Featured Post

Problems using Powershell and Active Directory?

Managing Active Directory does not always have to be complicated.  If you are spending more time trying instead of doing, then it's time to look at something else. For nearly 20 years, AD admins around the world have used one tool for day-to-day AD management: Hyena. Discover why

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Title # Comments Views Activity
Exchnage 2013 Database - Dirty Shutdown 4 104
Mailbox Permissions O365 5 57
exchange 16 49
NLB +DAG 8 54
Learn to move / copy / export exchange contacts to iPhone without using any software. Also see the issues in configuration of exchange with iPhone to migrate contacts.
A list of top three free exchange EDB viewers that helps the user to extract a mailbox from an unmounted .edb file and get a clear preview of all emails & other items with just a single click on mailboxes.
This video demonstrates how to sync Microsoft Exchange Public Folders with smartphones using CodeTwo Exchange Sync and Exchange ActiveSync. To learn more about CodeTwo Exchange Sync and download the free trial, go to: http://www.codetwo.com/excha…
This video shows how to quickly and easily add an email signature for all users on Exchange 2016. The resulting signature is applied on a server level by Exchange Online. The email signature template has been downloaded from: www.mail-signatures…

739 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question