Re: Combating directory harvests

[Roger A Safian <r-safian () NORTHWESTERN EDU>]

It's getting more difficult to contain this data as more means become available for accessing it, but generally, we 
limit the returns to a search to 20 (or is it 25?) unique responses.  Off campus searches have the email address 
obscured in a capcha like fashion.  We used to manage our logs better in the past and would black list IP's that were 
obviously scraping our directory.  We don't have the time to do this anymore.  We have been replying on our anti-spam 
and proactive education solutions to prevent phishing.  The number of victims remains low, so on some level I'd like to 
think our efforts are working, but, we may just be lucky.

> -----Original Message-----
> From: The EDUCAUSE Security Constituent Group Listserv
> [mailto:SECURITY () LISTSERV EDUCAUSE EDU] On Behalf Of Tyler T. Schoenke
> Sent: Thursday, July 19, 2012 2:44 PM
> To: SECURITY () LISTSERV EDUCAUSE EDU
> Subject: [SECURITY] Combating directory harvests
>
> I am wondering what other schools are doing to combat LDAP directory
> harvests.  We are constantly hit with phishing campaigns.  While some email
> addresses are grabbed via web searches, malware reading address books, or
> other means, I suspect email directory harvests account for a large
> percentage of the addresses used in phishing campaigns.
>
> Some ideas we have tossed around for limiting the harvests are:
>
> - Only allow email look-ups to campus address space and campus VPN.
>
> - Rate limit using a firewall or IDP to block an IP address for specific period of
> time if connection attempts are made too rapidly.
>
> - Rate limit at the web server that interfaces into the LDAP server.
> Only allow a specific number of queries per source IP address per time
> period.
>
> - Use a Captcha to reduce the number of automated queries.
>
> - Reduce the number of results returned.  Instead of 100 rows, return 5
> closest matches.
>
> - Require a valid email address to run the query.  Block email accounts from
> anonymous email providers.
>
> Has anyone implemented these or other measures to reduce LDAP harvests?
>  Are there any commercial solutions?
>
> Thanks,
>
> Tyler
>
> --
> --
> Tyler Schoenke
> Network Security Manager
> IT Security Office
> University of Colorado at Boulder