How Antivirus & Antispyware Work

by Billy J Long Guidance, PSA Articles

Article (PSA‑0004)

If a computer is connected to the Internet it is exposed to a constant stream of files, links, and network traffic. An up‑to‑date **antivirus/antispyware** solution provides the first line of defense by:

  • Scanning files in real time as they are downloaded or executed.
  • Running scheduled deep scans of the entire drive or selected folders.
  • Leveraging constantly‑updated threat definitions and heuristic/AI‑based detection.

Key features you should look for (2025)

  • Real‑time protection – automatically blocks malicious code before it runs.
  • Scheduled full‑disk scans – weekly or bi‑weekly deep scans.
  • Cloud‑based AI/behavioral analysis – catches zero‑day threats that signatures haven’t seen yet.
  • Automatic definition updates – at least daily.
  • Low system impact – runs efficiently on modern hardware without excessive RAM or CPU usage.

Built‑In Windows Options (Free)

  • Windows 10/11 – Microsoft Defender (formerly Windows Defender). Integrated, automatically updated, and provides both antivirus and antispyware protection at no extra cost.
  • Windows 7 – Microsoft Security Essentials (no longer supported after Jan 2020). If you are still on Windows 7, upgrade to a supported OS or use a third‑party solution, because Microsoft no longer provides definition updates for Windows 7.

Third‑Party Solutions (When You Need More)

For businesses or users who want additional features (e.g., ransomware‑specific protection, web‑filtering, centralized management), consider reputable vendors such as:

  • Bitdefender GravityZone
  • Kaspersky Endpoint Security
  • SentinelOne
  • Maldetect + ClamAV (for Linux/UNIX environments)

Why One Antivirus Is Enough

Running more than one real‑time AV/antispyware engine on the same machine creates problems:

  1. Resource contention – Each engine consumes RAM and CPU; the system may start paging to disk, drastically slowing performance.
  2. Software conflicts – Two scanners can flag each other as malicious, leading to false positives, constant alerts, or even system instability.
  3. Self‑quarantine – One product may quarantine the other’s core files, corrupting the second product and making it difficult to repair.
  4. Licensing overhead – Multiple subscriptions increase cost and administrative effort.

In short, **one well‑chosen, continuously updated product plus a firewall** gives you comprehensive protection without the downsides.

How to Detect an Infection

  • Frequent pop‑ups, unexpected toolbars, or strange system notifications.
  • New icons, programs, or services appearing without your consent.
  • Home‑page changes, unwanted redirects, or DNS hijacking.
  • System slowdown, frequent freezes, or crashes during routine tasks.
  • Unusual outbound network traffic (check with a network monitor or firewall logs).

Step‑by‑Step Response If You Suspect Malware

  1. Update definitions – Ensure both AV and antispyware engines have the latest signature database.
  2. Run a full system scan – Allow the scan to complete; it may take 30 minutes to several hours depending on data size.
  3. Follow the removal instructions – Quarantine or delete the identified items, then reboot if prompted.
  4. Re‑scan – After the reboot, run another full scan to confirm the system is clean.
  5. Check startup items & scheduled tasks – Use msconfig (Windows) or systemctl (Linux) to verify nothing suspicious is set to launch automatically.
  6. Change passwords – If you suspect credential theft, reset passwords on a clean device, especially for email, banking, and admin accounts.
  7. Restore from backup (if needed) – If the infection cannot be fully removed, revert to a known‑good backup.

When Professional Help Is Needed

If the malware persists after multiple scans, re‑appears after a reboot, or has caused system instability, you should consult a qualified IT service provider. PSA Computer Services offers a **“no‑fix, no‑pay” guarantee** – you only pay for successful remediation.

Best‑Practice Checklist

  • Enable built‑in Windows Defender (or a reputable third‑party solution) with real‑time protection.
  • Keep OS and all applications patched – enable automatic updates.
  • Schedule weekly full scans and daily definition updates.
  • Use a hardware or software firewall with inbound blocking and outbound monitoring.
  • Practice safe browsing: avoid unknown links, verify SSL certificates, and use a reputable browser.
  • Back up critical data using the 3‑2‑1‑0 rule; test restore procedures quarterly.
  • Enable multi‑factor authentication on all cloud accounts.

Bottom Line

No home or business should operate without a modern, regularly updated antivirus/antispyware solution and a firewall. One well‑maintained product, coupled with common‑sense habits (patching, backups, MFA), provides strong protection without the performance penalties and conflicts of running multiple overlapping tools.

Need a Reliable Antivirus Solution or a Clean‑Up?

Call PSA Computer Services at (707) 506‑6228 for a free assessment, installation, or infection remediation. We’ll get you protected quickly and affordably.