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A simple Ruby interface for CYMRU's DNS virus blacklist. See:
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Virus Blacklist

This is a simple Ruby interface for CYMRU's DNS virus blacklist.


This gem takes in the MD5 hash of a file and looks it up using CYMRU's DNS-based blacklist. Its usage is simple:

require 'virus_blacklist' 
require 'digest'  

file = '/path/to/file'  # Pick some file to scan  
hash = Digest::MD5.hexdigest( # Create an MD5 hash for it  

VirusBlacklist.resolver.query_timeout = 5   # Configure our Dnsruby::Resolver 
VirusBlacklist.scan(hash)   # Returns :safe :unsafe :unknown or :error  
VirusBlacklist.is_ok?(hash) # False if scan returns :unsafe, true otherwise  
VirusBlacklist.probe(hash)  # Returns a string like "1277221946 79" (or nil) 
                # 1277221946 is the Unix timestamp the virus was last seen
                # 79 means that 79% of anti-virus programs tested detected it
                # Nil means there's no data on that file.


This uses the Dnsruby gem to do DNS resolution. You can access the Dnsruby::Resolver object at VirusBlacklist.resolver in order to set any of its options as demonstrated above where we set the query timeout to 5 seconds. See the Dnsruby documentation for further information.

It also depends on the availability of CYMRU's service. People who abuse that may end up blocked or rate limited. The maintainer of this gem is not affiliated with them in any way and cannot help you with any service outages.

Please also note that their service is only free for non-commercial use and that they may apply other terms and conditions to the service.


Most non-virus files will come up as :unknown and DNS timeouts may cause scan to return :error so this does not provide much security. Changing even one bit of a malicious file will change the MD5 hash. At most, this might help curtail the spread of files known to be malicious, but it provides absolutely no assurance that a file is safe. Whether or not that is better than nothing depends on whether or not it lulls you into a false sense of security.


This uses a modified MIT license. The only change is that you don't have to worry about preserving the copyright notice or license file.

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