Unable to Network print - Invalid checksum

Question

I'm unable to print to a network printer. The firewall log shows that spoolsv.exe to the remote printer port is blocked because of an Invalid Checksum, it's coming from localhost(any).

I've tried searching the computer for all instances of spoolsv.exe and have added it to the checksum list in the firewall configuration, since the log doesn't tell me the file path of the specific application it blocked... I've also ensured that the LAN IP address of the printer is added to the trusted list.

Neither works - when I allow all traffic I can print without any problem, so the firewall is definitely the culprit here.

I'd be grateful for any suggestions?

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AlexC · Accepted Answer

Hello all, Solved my problem but thought to post here for sake of documenting and to save wasting anyones time replying. To determine the active process, go into Services under Administrative Tools and then find Print Spooler - open this and it will show the location of the spoolsv.exe. Add this to the checksum list in firewall configuration (remove any other spoolsv.exe in the list first), then also add it to trusted applications and hidden processes. I also added a Global Rule to allow outbound TCP to the remote IP address and port specified in the firewall block log rule when I experienced problems. Not sure which of the three things I applied is the actual solution, haven't got time to play about and find out now, but hope to do so soon! :3019