Norton Internet Security 2012 achieved a top rating of AAA in the latest Dennis Technology Labs Home Anti-Virus Protection test. What is significant about this test is that it is a "real world" test that looks at all of the protection features contained in a product, rather than just simply testing a product's ability to recognize specific threats. In other words, features that provide early warning of danger, such as Norton's reputation-based Download Intelligence, are factored into the results along with the usual Auto-Protect signature and heuristics protections. The test therefore provides a more accurate measure of how well a product will actually protect you in the types of situations where you are likely to encounter threats, such as exploit packs, in the real world.
http://dennistechnologylabs.com/reports/s/a-m/2012/
Security company, Sophos has posted an article on their blog discussing the Dennis Technology Lab methodology used in these tests. Sophos points out that although malware attacks frequently occur in four stages, most tests only measure protection that kicks in at the final stage. The Dennis tests look at the defenses provided by a product at all stages of an attack. The blog post concludes that such tests, which are "properly executed and look at the whole security solution, rather than just some of the components" provide a good indicator of how well a product can actually protect a user's system.
Comparative anti-malware tests: the RIGHT way to do them