KTS 2021 included a VPN module (powered by Kaspersky’s own infrastructure). However, version 21.3.10.391 only provided 200 MB to 300 MB of traffic per day for free. To lift the cap, you needed a separate subscription to Kaspersky VPN Secure Connection.
In controlled tests conducted in May 2021 on a Core i5-10400, 16GB RAM, Windows 10 20H2:
Build 21.3.10.391 introduced optimizations to ensure that security did not come at the cost of system speed.
If you are installing version 21.3.10.391 on an old machine, these are the requirements:
| Component | Minimum Spec | | :--- | :--- | | OS | Windows 7 SP1 (with ESU support), Windows 8.1, Windows 10 (20H2) | | RAM | 1 GB (32-bit) / 2 GB (64-bit) | | Disk Space | 1.5 GB free | | Processor | 1 GHz | | Screen | 1024 x 768 (for the GUI to render properly) | Kaspersky Total Security 2021 21.3.10.391 for W...
Warning for modern users: This version will install on Windows 11, but due to Microsoft's security changes (Virtualization-Based Security, Hypervisor-protected Code Integrity), you may experience performance glitches or a warning that the software is "Not fully compatible."
The interface in this build was a refinement of the 2020 aesthetic. It used a "metro-style" tile layout.
Pros of the UI:
Cons:
Before you commit to using this legacy version in 2024/2025, know the downsides:
Kaspersky Total Security 2021 version 21.3.10.391 for Windows was a high-water mark for consumer cybersecurity. It successfully argued that you don't need to sacrifice CPU cycles for safety. The inclusion of a Password Manager and Backup tool made it a true "total" package, eliminating the need for separate subscriptions.
For those running legacy hardware on Windows 10 (and who cannot upgrade to Windows 11), this version, provided you can manually update the virus definitions, remains a viable fortress. However, for modern PCs, you should seek the latest version (e.g., Kaspersky Plus 2025) to ensure protection against today's AI-generated malware and ransomware gangs.
Final rating (in its 2021 context): 9.2/10 Final rating (for use in 2026): 3/10 (only due to outdated engine, not quality) KTS 2021 included a VPN module (powered by
Before diving into features, it is crucial to ensure your hardware could handle this version. For 2021 standards, the requirements were modest, making it ideal for aging laptops.
Minimum Requirements:
The Installation Experience: Version 21.3.10.391 streamlined the installation to under two minutes. One notable feature during the setup was the "Installation Assistant," which scanned for conflicting security software (like McAfee or Norton remnants) and removed them automatically. The installer weighed approximately 180 MB.