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Insider threats are the cyber risks that live behind your login screen. They are not always malicious or obvious. An insider threat is any security incident caused by someone with legitimate access to your organization’s systems, data, or facilities. That can mean an employee, contractor, intern, vendor, or even a well-meaning volunteer. If they can log in, badge in, or touch sensitive information, they can become the source of a breach.
For small businesses and local governments, insider threats are especially dangerous because teams are lean, duties overlap, and trust is often informal. You may have one person who “does all the tech,” one person who handles payroll, and a handful of shared accounts that have existed for years. That environment is efficient, but it can quietly create a perfect storm: too much access, too little oversight, and not enough guardrails when something goes wrong.
The three types of insider threats
1) Malicious insiders
This is what most people picture: someone stealing data, sabotaging systems, or leaking information out of spite, financial motive, or pressure from outside criminals. Examples include exporting customer lists before quitting, planting malware, deleting files, or sharing confidential records with unauthorized parties.
2) Negligent insiders
These are the everyday mistakes that lead to major incidents. Clicking a phishing link, reusing passwords, sending sensitive files to the wrong recipient, misconfiguring cloud storage, or using personal devices and accounts for work. Negligent actions are the most common and often the most preventable.
3) Compromised insiders
Sometimes the “insider” is actually an outsider wearing a real user’s credentials. If an attacker steals an employee’s password, session token, or MFA approval, they effectively become an insider. That is why credential theft and social engineering are so closely tied to insider-threat defense.
Why insider threats happen
Insider incidents often come down to a few predictable drivers:
- Excessive access: People accumulate permissions over time and never lose them.
- Shared accounts: “Everyone uses the same login,” which eliminates accountability.
- Weak offboarding: Departing employees keep access for days or weeks.
- Low visibility: No logging, no alerts, and no one reviewing access activity.
- Lack of training: Staff do not know what real-life attacks look like.
- High stress or conflict: Performance issues, layoffs, and culture problems raise risk.
None of this requires bad people. It requires normal people operating in systems that are not designed to fail safely.
The warning signs worth paying attention to
Insider threats are not always dramatic, but patterns matter. Watch for:
- Unusual logins at odd hours or from unexpected locations
- Large, sudden downloads of files, especially outside of job duties
- Repeated access attempts to restricted systems
- Use of unauthorized storage (personal email, personal cloud drives)
- Disabling security tools or “working around” policies
- Employees expressing unusual resentment or talking about “getting even.”
- Vendors requesting broader access than their scope requires
These signs do not prove wrongdoing, but they justify a closer look and tighter controls.
Practical insider threats defenses that work in real organizations
You do not need a massive budget to reduce insider risk. You need repeatable basics.
1) Enforce least privilege
Give people access only to what they need for their current role. Review permissions on a schedule, not just when something feels wrong. A simple quarterly access review can prevent years of accumulated over-permission.
2) Kill shared accounts
Every user should have their own login. This is one of the fastest ways to improve accountability and investigation capability. If a system cannot support unique accounts, treat it as a high-risk system and plan an upgrade.
3) Make offboarding immediate and checklist-driven
Departures are a prime window for insider incidents. Your offboarding checklist should include:
- Disable user accounts and revoke tokens immediately
- Remove access to email, VPN, cloud storage, payroll, and admin panels
- Transfer ownership of files and shared resources
- Change shared passwords if they exist (and then eliminate them)
- Collect devices and verify that data is backed up and secured
If HR, IT, and management are not aligned, delays happen, and delays create risk.
4) Use strong authentication everywhere
Require MFA for email, cloud apps, remote access, and admin accounts. Where possible, use phishing-resistant methods such as security keys or passkeys. This dramatically reduces the number of “compromised insider” incidents.
5) Log what matters and review it
You cannot detect insider threats if you cannot see activity. At minimum, log:
- Authentication events (logins, failed attempts, MFA prompts)
- File access and sharing activity
- Admin changes (new accounts, permission changes, security settings)
- Endpoint security alerts
Even basic alerting on “mass download” or “new admin created” can stop a breach early.
6) Train staff with realistic scenarios
Training is not about fear. It is about pattern recognition. Teach staff how insider and impersonation attacks look:
- Phishing that requests urgent document access
- “CEO fraud” and fake invoice requests
- Vendor impersonation asking for password resets or access changes
- Requests to move files to personal accounts “for convenience.”
Train people to pause, verify, and report.
7) Build a culture of reporting
Employees should feel safe reporting mistakes quickly. The faster you learn about a wrong email recipient, a suspicious link, or a compromised account, the more damage you can prevent. If people fear punishment, they hide problems until they become incidents.
Insider threats response: what to do when you suspect an issue
If you suspect an insider threat, focus on containment and evidence preservation:
- Limit access immediately without tipping off the suspect unnecessarily
- Preserve logs, emails, and system records
- Involve HR and legal early for employee-related issues
- Document actions and timelines
- Consider engaging a forensics or incident response partner if data exposure is possible
- If government or regulated data may be involved, follow the required notification rules
Do not rush to blame. Verify activity, confirm scope, and follow your process.
Insider threats are not a sign that you cannot trust your people. They are a reminder that trust is not a security strategy. Strong organizations combine trust with structure: least privilege, clear onboarding and offboarding, strong authentication, basic monitoring, and a culture that encourages reporting.
If you implement those fundamentals, you reduce the risk from malicious insiders, negligent mistakes, and stolen credentials simultaneously. That is the real win: fewer incidents, faster detection, and much less damage when something goes wrong.
At Commonwealth Sentinel, we stay focused on cyber security so you can focus on other things. Contact us today or sign up for a free consultation.