To find out, we compared how good each is at catching malware, while also studying their feature sets and testing their performance impact on a computer system. In addition, we gave their user interfaces a serious examination.
After multiple rounds of comparison, Bitdefender Antivirus Plus (starting at $29.95) comes away with a conclusive victory, thanks to its perfect malware-detection rates, low system impact and easy-to-understand interface.
To measure how capable each of these programs is at detecting malware, we've used results from two independent product-testing labs, AV-TEST in Germany and AV-Comparatives in Austria. These companies regularly test products from about 20 leading antivirus brands by throwing a tsunami of malware at computer systems, then measuring how many files are caught and how many go undetected.
Almost every month, AV-Comparatives exposes computers running 64-bit Windows 7 to the latest online malware in what the lab calls its "real-world" protection tests. AV-TEST uses two benchmarks: It attacks systems with brand-new "zero-day" malware that hasn't been seen before, but also subjects computers to "widespread" malware discovered and identified in the previous four weeks. Its evaluations last two months apiece, and rotate among 32-bit Windows 7, 64-bit Windows 8.1 and 64-bit Windows 10.
The Bitdefender and Kaspersky Lab products tested by both labs were not the exact ones we’re comparing here. Instead, they were the "intermediate" suites, Bitdefender Internet Security and Kaspersky Internet Security, which offer several more features than their cheaper counterparts. But because each brand uses one malware-detection "engine" for all its Windows products, the protection results should be the same across a product line.
Bitdefender earned four flawless, 100 percent detection rates in AV-TEST's January and February 2016 Windows 7 evaluations against both zero-day and widespread malware. Kaspersky netted only three perfect marks, detecting 99 percent of zero-day malware in February. Neither brand registered any false positives ─ i.e., benign items mistakenly tagged as malware.
Bitdefender secured three 100-percent detection rates on Windows 8.1 in AV-TEST's November and December 2015 reports, detecting only 99.9 percent of widespread malware in November. Kaspersky earned only two 100-percent marks, detecting 97.5 percent of zero-day malware in November and 99.9 percent of widespread malware in December. Kaspersky had no false positives, while Bitdefender had one.
Bitdefender scored three 100 percent detection rates on Windows 10 in AV-TEST's September and October 2015 reports, detecting 99.9 percent of widespread malware in October. Kaspersky caught 100 percent of zero-day malware in both months, but 99.8 percent of widespread malware in September and 99.9 percent in October. Neither brand registered any false positives.
In AV-Comparison's March 2016 tests, Bitdefender caught 100 percent of malware and detected one false positive, while Kaspersky caught 99.1 percent and raised two false flags. One month earlier, Bitdefender caught 99.7 percent of malware and Kaspersky earned a flawless 100 percent detection date, with neither registering any false positives.
Winner: Bitdefender Antivirus Plus. Kaspersky is good, but Bitdefender is better.
Ease of use and of installation
Bitdefender Antivirus Plus and Kaspersky Anti-Virus share similar installation processes, but they differ in their interface designs. If you download the software and pay online with a credit card, either one will sign you up for automatic renewal, charging your card again when your paid subscription expires. This feature is either a convenience or an annoyance, depending on your perspective, but it can be disabled after installation.
Each suite's installation process takes about 5 to 6 minutes and is spread out over two sections. Both programs offer rescue disks that can be downloaded and burned to optical disks or installed on USB drives. But Bitdefender also creates a hidden rescue partition on older computers without Microsoft’s Secure Boot feature.
Both programs offer status updates on their home screens, but Bitdefender Antivirus places its scans one click away from that screen, while Kaspersky Anti-Virus buries its scan buttons under several pages. Bitdefender also places a handy status widget in the bottom right of the desktop that can run all the time.
If that wasn't enough to give Bitdefender the win, Kaspersky's poorly organized layout dooms it in our eyes. The Kaspersky screens look slapped together, filled with white space that wastes real estate. Bitdefender Antivirus has a well-composed layout that puts more controls in front of the user.
Winner: Bitdefender Antivirus Plus. It looks friendlier and is easier to use.
System performance impact
We measured the impact that Bitdefender Antivirus Plus and Kaspersky Anti-Virus had on our budget laptop by timing how quickly our OpenOffice benchmark test finished, both after each program was installed and during active scans. The OpenOffice test checks how quickly a system can match 20,000 names to 20,000 addresses.
Neither program slowed our test system (an Asus X555LA laptop with an Intel i5-4005U CPU running Windows 8.1 with 6GM of RAM) while each ran in the background. But we saw different performance speeds while active scans were running.
During a Bitdefender full scan, the OpenOffice test finished its test in 7 minutes and 48 seconds, a 13 percent slowdown from the baseline of 6:53. During Kaspersky's full scan, our benchmark finished in 8:18, a full 30 seconds longer than the Bitdefender text, indicating a 21 percent system slowdown.
Bitdefender scored another win during a quick scan, during which the OpenOffice test finished in 6:58, only 1 percent slower than the baseline. During the Kaspersky full scans, the test finished in 7:14, 5 percent slower than the baseline.
Winner: Bitdefender Antivirus Plus. Kaspersky doesn't impact performance much, but Bitdefender takes up even fewer resources.
Bitdefender Antivirus Plus and Kaspersky Anti-Virus each offer plenty of security features. One of the most important is a dedicated defense against ransomware, and while both products offer some protection, one is less complete.
Both Bitdefender and Kaspersky have defenses against screen-locking ransomware, so attackers can't kick you out of your computer with a splash-screen that demands you send a fee over PayPal or in Bitcoin. Only Bitdefender, though, aids users by pre-emptively locking down files designated by the user so they can't be turned into gibberish by file-encrypting ransomware.
Both Kaspersky Anti-Virus and Bitdefender Antivirus Plus offer virtual keyboards to users, a safety measure that stops keyloggers from collecting records of what you've typed. Bitdefender's Safepay is a secure web browser for online banking and shopping, and protects users by limiting extensions and disabling screenshots. Kaspersky Anti-Virus offers no such browser.
Winner: Bitdefender Antivirus Plus. It offers more useful features.
Each of these antivirus solutions offer features that may not protect you, but are handy. Both Bitdefender Antivirus Plus and Kaspersky Anti-Virus offer a "game mode" so you can play a game or watch a movie without the program interrupting your activity.
Bitdefender also gives users a file shredder for the secure deletion of sensitive material, and a password manager that allows you to create and manage complex, hard-to-crack passwords. Kaspersky Anti-Virus includes neither of these perks, though its more expensive sibling ─ Kaspersky Total Security ─ does.
Winner: Bitdefender Antivirus Plus. Having a built-in file shredder and password manager give it the edge.
While Kaspersky Anti-Virus is a solid antivirus solution, Bitdefender Antivirus Plus is superior across the board. Not only does Bitdefender detect more malware, but it doesn't impact system performance as much. And on top of that, Bitdefender Antivirus Plus ($29.99 per year) gives you more extras and a better interface than Kaspersky Anti-Virus ($34.99 per year) for less money.
[Editor's Note, Sept. 11, 2017: Best Buy has removed Kaspersky Lab products from its shelves, citing concerns regarding Kaspersky's alleged (but as yet undocumented) ties to the Russian government. However, until we see evidence that Kaspersky software is a threat to consumers, we will continue to recommend it. Here is further clarification of our position.]