This is not an official Valve release. It is a heavily modded version of the original Counter-Strike (likely built on the GoldSrc engine) designed to look and feel like a hybrid between CS 1.6 and CS:GO. It is popular in regions like South America and Eastern Europe where low-end PCs are common.
"Fire in the hole!" a bot shouted, the sound file crackling with low-bitrate distortion. counter strike 18 goiceasoft portable