Advanced Persistent Threat (APT): What it is, how it works, and how to defend against it

APT (Advanced Persistent Threat)

What it is

An APT is a long-game, targeted attack. Skilled attackers quietly break in, move sideways through the network, and stay hidden for weeks or months to steal sensitive data—not to make noise. Think careful recon, staged break-ins, and patient data theft. Learn more in our 
APT guide
.

How it works 

  • Initial access: spear-phishing, stolen credentials, or a zero-day.

  • Persistence & stealth: “living off the land” tools, scheduled tasks, legit admin utilities.

  • Lateral movement: hop between systems, escalate privileges, map crown jewels.

  • Exfiltration: compress, stage, and quietly send data out.

What you might notice

  • Unusual admin logins at odd hours

  • New scheduled tasks, services, or remote connections

  • Legit tools (PowerShell, PsExec) used in suspicious ways

  • Data spikes to unknown destinations

If you suspect an APT 

  1. Isolate affected systems; don’t tip off the attacker with broad resets.

  2. Collect evidence (logs, memory, timelines) before changes.

  3. Reset creds from a clean host; rotate keys/tokens.

  4. Hunt laterally—assume multiple footholds.

  5. Engage IR specialists and notify stakeholders as required.

Strengthen your defenses

  • EDR/XDR + threat hunting; enable detailed logging (auth, PowerShell, DNS, proxy).

  • MFA everywhere, least privilege, and privileged access workstations.

  • Patch fast on internet-facing apps; inventory and segment critical data.

  • Email and identity security: protect against spear-phishing and token theft.

  • Practice: tabletop exercises and restore drills for backups.

    Glossary (A–Z)

    All A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

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