: Standard Blizzard installs require at least one online authentication before allowing offline play, a hurdle that many cracks attempt to bypass using modified launchers like SC2ALLin1. Security Risks

: Files from unverified third-party sources often contain malware or trojans designed to steal account data.

Before searching for unofficial installers, note that the official client already provides a massive amount of content for free:

Which of those would you like?

The full first single-player campaign is entirely free.