Quarantining infected hosts (Was: FBI tells the public to call their ISP for help)

Leigh Porter leigh.porter at ukbroadband.com
Tue Jun 19 23:55:38 UTC 2007

Douglas Otis wrote:
> On Jun 19, 2007, at 8:35 AM, Suresh Ramasubramanian wrote:
>> On 6/19/07, Leigh Porter <leigh.porter at ukbroadband.com> wrote:
>>> Agreed, SMTP is not really a special vector, other than it's obvious 
>>> commercial spam use. So just block all the usual virus vector ports, 
>>> block 25 and force people to use your own SMTP servers and the 
>>> problem [for] this particular one goes away..
>> No. the part of it you target (outbound spam) merely relocates 
>> itself, and your smtp servers become huge spam sinks.  Filter all you 
>> want and you'll still leak spam unless you take those hosts down
>> And in the meantime those hosts will also be launching dos attacks, 
>> hosting "fast flux" pills / warez / kiddy pr0n sites, carrying out id 
>> / card theft .. best to isolate and take them down.
>> You can port block at your edge till you burst and you'll still be in 
>> a lot of hot water.
> Web-site/browser vulnerabilities make ISP efforts largely futile.  
> Infection rates easily overwhelm aggressive automated detection and 
> wall-garden strategies.  Nevertheless, blocking port 25 offers several 
> benefits even for this seemingly failing effort.  Messages can be rate 
> limited, where delivery errors also provide direct clues as to which 
> system are likely infected.
> Web related script vulnerabilities impact some of the largest online 
> email providers!  In the zeal to enable advertising, customer accounts 
> are easily harvested.  These accounts may also receive password 
> updates from other accounts, placing even critical financial 
> information at risk.  Every compromised account is then able to 
> impersonate owners, utilize their address book and entice further 
> infections by offering malware related messages.  The malware might 
> appear as seemingly harmless links or documents.  Email is a vector 
> that must be watched carefully, however the greater danger is with 
> web/browser vulnerabilities.
> Complacency permitting, and at times even promoting use of known 
> defective products must end.  The era of combining scripts and active 
> code along with every piece of information conveyed must end.  Unless 
> the Internet industry responds effectively, legislators will likely to 
> react in their own futile way.
> Less is more.  A document MUST NOT require active code to convey 
> information.
> -Doug
This is a great point Doug. Port based vulns are, IMO, starting to 
decline due to update of SP2 etc. There's still a lot there but in a few 
years it will be quite low as hopefully most people will either filter 
it or customers will have default on firewalls.

Browsers and dumb customers opening emails are where it's at now. The 
only way to filter that is to look at ALL traffic using some horrid DPI 
box or proxy or something.

life really sucks.


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