If you must download the files from a third-party source, scan the .exe or .dmg file with a tool like VirusTotal before installing.
To solve this, Adobe released a patch. If you are a legitimate license holder, you can download this offline activator from the Adobe help pages. This essentially tells the software to skip the server check and run locally. adobe cs3 download
Since activation servers are gone, you might need: If you must download the files from a