Change default router passwords and use WPA3 encryption.

Windows Security (Defender) is highly recommended for Windows users because it is free, pre-installed, and effective without excessive upsells. For broader protection or non-Windows systems, considered, reputable options include Bitdefender, Malwarebytes, and ESET.

Enable automatic updates for your operating system (Windows/macOS), browsers, and apps to patch security vulnerabilities.

Be cautious of "free" security software that turns out to be a paid trial or constantly nags with upsells.