You are a few updates behind, the last version for 6.3 was 6.3.18 and can be found here -> https://downloads.dynatrace.com/downloads/download...
I would definitely look to upgrade it as a lot of things have been fixed and improved.
Understood. You can see all the updates that were made by looking at the release notes -> https://community.dynatrace.com/community/pages/viewpage.action?title=Dynatrace+6.3.18+Release+Notes&spaceKey=PROD
If you search just for the keyword 'security', you'll find a decent amount of things were improved from 6.3.3 to 6.3.18.
Hope that helps,