BKAV used to be a pretty good antivirus in Vietnam, back in 90s. Back then its size was quite small (about 2MB) so it was often used in VN for quick removal of viruses. BKAV stands for Bach Khoa AntiVirus: Bach Khoa stands for Polytechnic University of Ha Noi, where Nguyen Tu Quang (BKAV's creator) worked as a Math teacher.
Unfortunately it's not that good anymore. The free version (BKAV Home & BKAV Home Plus) doesn't offer live update. Live update means that you have to download the whole new version of the program - similar to dr.web cureit! - which explains why BKAV isn't that useful anymore, as its size is growing larger and larger.
Besides, incompatibility problems with other antiviruses are often reported by users in VN. Kaspersky, for example, always flags BKAV as a trojan or something, the geeks at BKIS (BKAV's HQ) then adviced their users to install only BKAV as the main antivirus on their PCs, which, usually, leads to mass system re-installations (don't know why, maybe because BKAV often removes infected system files on system reboot without user's awareness).
That is the old story of BKAV. Recently BKAV has released BKIS 2015 (Bach Khoa Internet Security 2015), which is a totally-rewrited program. It claims to offer better protection than their long-lasted previous one. But BKIS 2015 doesn't offer any free-trial.
So I wouldn't recommend BKAV for regular uses.