The problems caused a flurry of angry posts to the Symantec area of support forums from users saying they would ditch Symantec's Norton AntiVirus. Users of the Norton products reported that their PCs locked up or slowed down after downloading the latest virus definitions on Wednesday and Thursday. Symantec itself reported that "after January 7th your computer slows down and Microsoft Word and Excel will not start."
But rather than Norton AntiVirus, Symantec said in a statement on its site that the problem "appears to be related to VeriSign receiving an unusual number of requests by Windows-based clients to download a certificate revocation list (CRL) on January 7-8, 2004. This increase in traffic resulted in intermittent VeriSign CRL server availability."
Norton AntiVirus products routinely verify the integrity of system components using certificates issued by VeriSign. Neither Verisign nor Symantec could immediately explain the exact sequence of events, but according to the statement on Symantec's site copies of Norton AntiVirus installed on PCs were unable to achieve the authentication they required due to the unavailability of VeriSign's server. "Therefore customers experienced delays and instabilities," said Symantec.
Hinting that it was not the only company whose products were affected, Symantec said it "and other vendors" were "cooperatively working with VeriSign to mitigate this situation."
Symantec issued a quick fix for the problem, which involves deselecting the option in Internet Explorer to check for publisher's certificate revocation.
Despite Symantec's protests that it is not to blame, the episode has created bad publicity for its Norton AntiVirus product. "I am now strongly tempted to trash Norton AV in favour of something more user-friendly and which doesn't slow down the opening of every damned thing in sight!" said one poster. "I have been having 16-plus second delays if I right-clicked on anything - even after a system reboot," wrote another. "I am not happy and have installed Sophos instead." This individual then went on to say they were not happy with that either "as updates seem incredibly confusing... I shall now try McAfee."
Update: Late on Friday, Verisign posted an explanation on its site, and said that the problem with the Certificate Revocation List, which affected Norton AntiVirus, was not connected to the Intermediate CA expiration issue, which caused problems for secure Web sites at about the same time last week.
The company said that requests to its server at crl.versiign.com suddenly increased one hundred-fold due to Windows clients trying to download the CRL. "We immediately took steps to increase capacity and determine the root cause," said VeriSign, and "within 24 hours, had increased capacity on crl.verisign.com ten-fold to handle this increased request load."
"VeriSign regrets any inconvenience that may have resulted from this period of increased demand," said the company in its statement. "In addition to increasing capacity, VeriSign has made certain modifications to the CRL distribution logic to more effectively handle subsequent wide-scale CRL downloads and continues to work with those that may have experienced response delays as a result of the increased demand. We also continue to work with industry leaders, partners, and the technical community to encourage promulgation the use of alternative validity determination mechanisms, such as the online certificate status protocol, which may be less susceptible to these kinds of periodic events."