Windows Firewall turned out to be one of the two most significant reasons (the other being DCOM activation security) that many corporations did not upgrade to Service Pack 2 in a timely fashion. Around the time of SP2's release, a number of Internet sites were reporting significant application compatibility issues, though the majority of those ended up being nothing more than ports that needed to be opened on the firewall so that components of distributed systems (typically backup and antivirus solutions) could communicate.