New service - the Team Cymru Malware Hash Registry!

Steve Freegard steve.freegard at
Tue Oct 28 22:35:16 GMT 2008

--[ UxBoD ]-- wrote:
> Steve, understood, but if a local persistant cache was generated then the number of upstream look ups for the same hash would reduce ? would this not also reduce the load on the upstream servers ? sorry if I am being stupid but it kinda makes sense to me :( isn't that what AV sigs are for ?

All the records from the Malware Hash Registry have a TTL of 86400 
seconds (24 hours), so that means that if you're looking up the same 
hash within 24 hours - it will come from your local cache provided it 
hasn't been purged to reclaim space.

If you maintain a local cache - you really don't save a lot of lookups 
to the upstream since the vast majority of lookups are going to be 
negative lookups (e.g. NXDOMAIN).

DNS was designed with caching in mind; and it works just fine for the 
purposes it was designed for - adding a second cache is almost always a 
bad idea and will introduce lag and incorrect results along with space 

If you're going to argue a local cache for these hashes - why not argue 
for local caching for DNS BL or URI BL lookups as well?  The reason we 
don't do local caching for these is exactly the same as why we shouldn't 
do it here - the data is fluid - there's no guarantee that a positive or 
negative lookup now yield the same result the next time you look at the 


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