On the occasion of 13 years of "Command & Conquer : Red Alert" (more precisely, 31 August 2008), Electronic Arts and Westwood Studios have given the possibility to download Red Alert 1 for free from their servers. The problem is that the official page listing links disappeared since. However, you can still download the archived version from the Electronic Arts (EA) download link.
Since the game was made free by Electronic Arts, it is still legal.

Allied disc download

• ea.com - Official server of Electronic Arts (via archive.org)
• abandonware-france.org

Soviet disk download

• ea.com - Official server of Electronic Arts (via archive.org)
• abandonware-france.org

Also download other games "Command & Conquer" free and legally :
- Command & Conquer
- C & C Tiberium sun and its extension Mission Hydre