Detecting and Protecting Against Insider Attacks

What Are Insider Attacks?

Insider attacks happen when employees, contractors, or third-party partners misuse their access to harm the organization. Unlike hackers breaking in from the outside, insiders already hold legitimate credentials and knowledge of systems. This makes their actions harder to detect and often more destructive.

An insider attack is a cybersecurity incident where someone within the organization abuses their access rights. Protection requires monitoring tools, identity management, and privileged access controls.

Why Insider Attacks Are So Dangerous

Insider attacks are not typical cyber threats. They originate from trusted individuals who already have access to sensitive systems and data. This unique position makes insider threats stealthy, hard to identify, and highly damaging.

Trusted Access: Insiders can bypass external security layers

Unlike external hackers who must break through firewalls or crack passwords, insiders already have legitimate access to corporate networks. This allows them to move freely without triggering perimeter defenses.

Example:

In 2020, a former Cisco employee used still-active credentials to access the company’s cloud environment and deleted 456 virtual machines. No hacking tools were required — only insider access.

Hard to Detect: Malicious activity often resembles routine work

Insiders know how to blend in with normal workflows. Copying files, running queries, or downloading reports may look like everyday tasks, making it difficult for monitoring tools to flag suspicious behavior.

Example:

Edward Snowden, an NSA contractor, copied thousands of sensitive documents under the guise of regular system access. For months, his activities looked like part of his job, delaying detection.

High Cost: Breaches often involve sensitive intellectual property or customer data

When insiders abuse their access, the damage is often greater than with external breaches. They target high-value data — financial records, source code, or customer information — that can lead to lawsuits, fines, and reputation loss.

Example:

In 2019, an insider exploited knowledge of Capital One’s cloud setup to steal personal data from over 100 million customers. The breach cost the company hundreds of millions in fines and settlements.

Expanding Risk: Remote work and third-party vendors increase exposure

The rise of remote work and reliance on contractors means more people have at least some level of access to internal systems. Every additional endpoint or vendor account increases the risk of insider misuse or compromise.

Example:

In the Target breach of 2013, attackers gained access to the retailer’s network by compromising credentials from a third-party HVAC contractor. While not a traditional employee, this “insider by extension” opened the door to a massive credit card data breach.

Common Types of Insider Threats

Not all insider threats are the same. Some insiders act deliberately, while others cause harm by accident. Understanding these categories helps build tailored defense strategies.

Malicious Insiders

A malicious insider is an employee, contractor, or partner who deliberately uses their access to harm the organization. Their motives vary — revenge after termination, financial gain, espionage, or competitive advantage.

Why it’s dangerous:

• They already know the organization’s weak points, processes, and security gaps.

• They can exploit trust and privileged access to bypass security systems.

• Damage is often intentional and highly targeted (e.g., stealing intellectual property, erasing critical data, leaking confidential records).

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How it happens:

• Copying sensitive files before leaving the company.

• Selling trade secrets to competitors.

• Sabotaging systems by deleting or modifying data.

Example:

A pharmaceutical company employee planning to join a competitor leaked drug formula research. Because the insider had authorized access to R&D systems, no alarms were triggered during the data transfer.

Negligent Insiders

Negligent insiders are employees who do not intentionally harm the company but cause security breaches through mistakes, lack of awareness, or carelessness.

Why it’s dangerous:

• They make up the majority of insider incidents (often over 60% in reports).

• Their actions can open the door to external attackers.

• It’s difficult to “fix” negligence without strong training and monitoring.

How it happens:

• Clicking phishing links or downloading malicious attachments.

• Reusing weak or exposed passwords across systems.

• Mishandling sensitive data (e.g., sending files to personal email).

Example:

In 2017, a global shipping giant was hit by the NotPetya malware after an employee unknowingly clicked on a phishing email attachment. The malware spread rapidly, causing weeks of downtime and hundreds of millions in losses.

Compromised Insiders

A compromised insider occurs when an external attacker gains control of a legitimate user’s credentials or device. From the system’s perspective, the attacker “looks like” a valid employee.

Why it’s dangerous:

• Attacks are extremely hard to detect because all actions seem authorized.

• Compromised accounts can escalate privileges and move laterally across the network.

• Often used in ransomware or data exfiltration campaigns.

  
  

How it happens:

• Phishing attacks that capture login credentials.

• Credential stuffing attacks using passwords leaked on the dark web.

• Malware installed on an employee’s device, giving attackers remote access.

Example:

In many ransomware campaigns, attackers purchase employee logins from underground forums. With these credentials, they log into VPNs or remote desktops, deploy malware, and move inside the organization without being flagged.

How to Protect Against Insider Attacks

Least Privilege Access

Every user should only have the rights necessary to perform their tasks — nothing more. This prevents employees from accidentally or intentionally accessing sensitive systems they don’t need.

In 2018, a departing employee at a healthcare company accessed sensitive patient files because their account still had broad permissions. If least privilege policies had been enforced, the data exposure could have been avoided.

Multi-Factor Authentication (MFA)

Even if an insider’s password is leaked, MFA (such as SMS codes, authenticator apps, or biometrics) adds another barrier. It’s particularly critical for admin accounts and remote access.

Example:

In many ransomware attacks, compromised employee credentials are the entry point. Companies that enforced MFA often prevented attackers from logging in with stolen credentials.

Data Loss Prevention (DLP)

DLP solutions monitor and restrict attempts to move sensitive files outside the organization — through email, cloud storage, or USB drives. They also generate alerts when suspicious transfers occur.

Example:

A well-known case in the financial industry involved employees emailing confidential client data to personal accounts. DLP would have flagged or blocked these attempts before information left the network.

Security Awareness Training

Not all insider threats are malicious — negligence is a huge factor. Regular training helps employees spot phishing, social engineering, and understand the consequences of mishandling data.

Example:

In 2017, a major shipping company suffered downtime when an employee opened a phishing email, leading to malware installation. Proper training could have prevented the mistake.

Privileged Access Manager (PAM)

PAM tools ensure that administrative accounts — the “keys to the kingdom” — are tightly controlled. They provide session recording, just-in-time access, and approval workflows to prevent abuse.

Example:

In the Cisco insider incident (2020), a former employee used privileged credentials to destroy virtual machines. A PAM system could have revoked, monitored, or limited those credentials immediately after offboarding.

Identity and Access Management (IAM)

IAM enforces identity verification, centralizes access controls, and automates provisioning/deprovisioning of accounts. It ensures that only the right people have the right access, and it integrates with HR workflows to disable accounts quickly when employees leave.

Example:

In the Target breach (2013), attackers exploited credentials from a third-party vendor. A strong IAM framework with vendor access management and monitoring could have blocked or restricted that access.

Incident Response Playbooks

Even the best defenses can fail. An incident response (IR) playbook outlines step-by-step actions when suspicious insider activity is detected — who to notify, how to revoke access, and how to contain the damage.

Example:

During the Capital One breach (2019), the response involved forensic investigation and coordination with regulators. If a predefined IR playbook had been in place, detection and mitigation could have been faster.

Real-World Insider Breaches at a Glance

Edward Snowden (2013) — NSA Data Leak

Edward Snowden, a contractor working for the U.S. National Security Agency (NSA), had legitimate access to classified intelligence documents. He used his insider privileges to copy and extract thousands of files that revealed global surveillance programs. Snowden leaked this information to journalists, sparking worldwide debates about privacy, government monitoring, and cybersecurity.

Lesson: Even highly trusted insiders with top-level clearance can become whistleblowers or threats. Stronger monitoring of privileged users and better insider threat detection might have limited the scope of the leak.

Capital One (2019) — Cloud Misconfiguration Exploited

A former Amazon Web Services (AWS) engineer, Paige Thompson, exploited her knowledge of cloud infrastructure to identify a misconfigured firewall in Capital One’s AWS environment. She gained unauthorized access and stole sensitive data from more than 100 million customers, including names, addresses, credit scores, and Social Security numbers.

Lesson: Insider knowledge of cloud platforms combined with misconfigurations can be devastating. Stronger Identity and Access Management (IAM) controls and cloud security audits could have prevented the breach.

Cisco (2020) — Sabotage by Former Employee

A disgruntled former Cisco employee, after leaving the company, used valid credentials that had not been revoked to access Cisco’s cloud environment. He deleted 456 virtual machines, disrupting Cisco’s WebEx Teams service. The damage cost Cisco around $1.4 million in remediation and legal expenses.

Lesson: Failure to immediately revoke access after employee termination leaves organizations vulnerable. A Privileged Access Manager (PAM) and strict offboarding processes are critical.

Tesla (2021 Attempt) — Insider Bribery Plot

Tesla reported an incident where Russian cybercriminals approached an employee at its Nevada Gigafactory and offered $1 million to install ransomware on Tesla’s internal systems. The employee reported the bribery attempt to the FBI, which led to the arrest of one of the plot’s organizers.

Lesson: Attackers often try to “buy” insiders rather than hack from the outside. Insider threat programs and strong ethical awareness are crucial in discouraging and detecting such schemes.

Target (2013) — Vendor Compromise Led to Breach

The infamous Target breach began when attackers compromised credentials from a third-party HVAC vendor. These credentials allowed them to access Target’s internal network, which they then used to install malware on point-of-sale (POS) systems. The result was the theft of 40 million credit and debit card records and 70 million customer records.

Lesson: Vendors and contractors represent an extended insider risk. Strong vendor management, network segmentation, and Identity and Access Management (IAM) policies are essential to limit exposure.

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ESKA’s Insider Threat Protection Services

At ESKA Security, we provide:

• SIEM & UEBA integration for real-time detection of insider anomalies.

• PAM & IAM solutions to secure identities and privileged accounts.

• Red Team simulations to test insider threat scenarios.

• vCISO services for governance, compliance (SOC 2, ISO 27001, GDPR), and risk management.

• Incident Response services to contain insider-related breaches quickly.

Insider threats are among the hardest to detect, but the right mix of monitoring, identity management, and expert guidance makes them manageable. Talk to an ESKA expert.