According to latest test by independent security researchers AV-Comparatives, Microsoft’s Security Essential product was among the top-rated security software products.

The test pitted 16 different security products against 10 malware samples. Only six received an advanced-plus rating, including Security Essentials, reports Ghacks Technology News. Moreover, Microsoft's product was:

the only free product to score the highest rating and one of three that scored a good rating in the two tested fields of removal of malware and removal of leftovers.

As TECH.BLORGE notes:

This is a great result for Microsoft because it puts MSE on a par with the best paid-for products and ahead of both paid-for and free alternatives.