question

Hello,

Thank you for reaching to the Sophos Community!

You may refer to the below KBA:

https://docs.sophos.com/nsg/sophos-firewall/19.5/Help/en-us/webhelp/onlinehelp/AdministratorHelp/Applications/HowToArticles/BlockApplicationsUsingApplicationFilter/index.html

If you are looking any specific application, kindly share the details of the application name. We need to validate whether the signature of that application is exist with the current signature database or not.

Hello Samuel,

In addition to Mayur's recommendation above, You may also try blocking using File Types under Web > File Types 

https://docs.sophos.com/nsg/sophos-firewall/20.0/help/en-us/webhelp/onlinehelp/AdministratorHelp/Web/FileTypes/index.html

-Then under a specific Web Policy you are using, apply the File Type you have defined as per the step on the doc link above

Then configure and SSL/TLS inspection rule: https://docs.sophos.com/nsg/sophos-firewall/20.0/Help/en-us/webhelp/onlinehelp/AdministratorHelp/RulesAndPolicies/SSL/TLSInspectionRules/SSLTLSRules_AllowingNonDecryptableTraffic/index.html#introduction

Then install SF SSL certificate on client machine/s: https://support.sophos.com/support/s/article/KBA-000003689?language=en_US

Hope this helps. You have a nice day and thank you for choosing Sophos.

Cheers,