Not all security incidents look the same. An account you can no longer access is a different problem from a ransom note on your screen. Responding effectively depends on understanding what has actually happened.

This guide covers the six most common types of security incidents. For each one, you will find the warning signs to look for and the steps to take immediately. Prevention guidance follows for each, because the best time to prepare is before an incident occurs.

INCIDENT TYPE 01

Account Takeover

Someone has gained unauthorized access to one of your accounts. This may be an email account, a cloud application, a business tool, or a financial portal. Account takeovers are one of the most common entry points into broader security incidents. A single compromised login can give an attacker enough access to reset other passwords, impersonate staff, or move deeper into your systems.

Signs you may be affected

• You can no longer log in with your usual credentials
• You receive password reset emails you did not request
• Contacts report receiving unusual messages from your account
• Login activity shows access from unfamiliar locations or devices
• Account settings or recovery details have been changed without your knowledge

What to do immediately

1. Change the compromised password from a clean, unaffected device
2. Enable multi-factor authentication if it is not already active
3. Review all active sessions and revoke any you do not recognize
4. Reset passwords on any other accounts that share the same credentials
5. Notify contacts if your account was used to send messages on your behalf

How to prevent this

• Use a password manager to generate unique passwords for every account
• Enforce multi-factor authentication consistently across all critical systems
• Train staff to recognize phishing attempts before they interact with them
• Use breach alert services to monitor for leaked credentials

INCIDENT TYPE 02

Phishing and Business Email Compromise

Someone impersonated a trusted contact to extract sensitive information or authorize a fraudulent transaction. Business Email Compromise targets finance teams, executive assistants, and operations staff with requests that appear routine: invoice approvals, wire transfers, or changes to payment details.

Unlike ransomware, systems often remain fully operational. The damage is financial and reputational rather than technical, which is why it often goes undetected until funds have already moved.

Signs you may be affected

• A payment was authorized based on an email you now suspect was fraudulent
• An urgent financial request arrived from a known contact but the tone or details felt off
• Email headers show the sender domain does not match the displayed name
• A vendor confirms they never sent a payment request you acted on
• Someone internally received a request to update banking or payment details

What to do immediately

1. Stop any pending transfers and contact your bank to attempt a recall
2. Preserve all email evidence and do not alter or delete any communications
3. Notify internal leadership and your legal team as soon as possible
4. Report the incident to relevant financial institutions and authorities
5. Identify everyone who received or acted on the fraudulent communication

How to prevent this

• Implement email authentication standards: SPF, DKIM, and DMARC
• Use a secure email gateway with phishing detection capabilities
• Require secondary verification, verbal or in person, for all high-value transactions
• Run regular phishing simulations so staff can recognize attempts before they act

INCIDENT TYPE 03

Ransomware Attack

Malware has encrypted files or systems and is demanding payment for their release. In many cases, attackers also copy data before encrypting it and threaten to publish it. Operations can halt entirely. This type of incident has the most immediate and visible impact on business continuity.

Ransomware most commonly enters through phishing emails, unpatched software, exposed remote desktop services, or third-party vendor access. The technical entry point is often straightforward. The damage it causes is not.

Signs you may be affected

• Files have been renamed with unfamiliar extensions and cannot be opened
• A ransom note has appeared on screen as a text file or desktop wallpaper
• Systems are running unusually slowly or shutting down without explanation
• Security or antivirus tools have been disabled without your action
• Multiple staff members have lost access to shared drives or applications at the same time

What to do immediately

1. Isolate affected systems from the network immediately by disconnecting from Wi-Fi and unplugging ethernet cables
2. Do not attempt to pay the ransom without guidance from a security professional
3. Engage a cybersecurity incident response team as early as possible
4. Check the integrity of your backups before beginning any recovery attempt
5. Notify your legal, compliance, and leadership teams, as regulatory obligations may apply

Signs you may be affected

• Files have been renamed with unfamiliar extensions and cannot be opened
• A ransom note has appeared on screen as a text file or desktop wallpaper
• Systems are running unusually slowly or shutting down without explanation
• Security or antivirus tools have been disabled without your action
• Multiple staff members have lost access to shared drives or applications at the same time

INCIDENT TYPE 04

Data Breach

Sensitive information has been accessed, copied, or exposed without authorization. This may include customer records, financial data, intellectual property, or internal communications. Breaches can result from external attacks, insider threats, misconfigured cloud storage, or vulnerable third-party integrations.

The consequences extend beyond the technical event. Regulatory fines, legal exposure, and the loss of customer and partner trust are common outcomes, often more costly than the incident response itself.

Signs you may be affected

• Unauthorized or unusual access to databases, file storage, or cloud environments
• Customers or partners report receiving information they should not have
• Sensitive files have moved to unexpected locations or are missing entirely
• Security monitoring alerts flag large or unusual data transfers
• A vendor or partner notifies you of a breach on their end that involves shared data

What to do immediately

1. Identify the scope of the breach: what data was exposed, when, and through what access point
2. Close the vulnerability that allowed the breach with support from IT or a security firm
3. Notify affected stakeholders and regulatory bodies as required by applicable law
4. Engage forensic experts to document the incident for legal and insurance purposes
5. Set up identity monitoring for individuals whose data may have been exposed

Signs you may be affected

• Unauthorized or unusual access to databases, file storage, or cloud environments
• Customers or partners report receiving information they should not have
• Sensitive files have moved to unexpected locations or are missing entirely
• Security monitoring alerts flag large or unusual data transfers
• A vendor or partner notifies you of a breach on their end that involves shared data

INCIDENT TYPE 05

Malware Infection

Malicious software is running on your systems. Not all malware encrypts files or announces itself. Many infections operate silently, collecting credentials, redirecting traffic, or creating persistent backdoors for future access. You may not notice anything is wrong until significant damage has already been done.

Common entry points include malicious downloads, compromised websites, unsafe browser extensions, and infected USB devices. User behavior plays a role, but so do gaps in endpoint protection and software update policies.

Signs you may be affected

• Devices are running unusually slowly, overheating, or behaving erratically
• Unexpected pop-ups, browser redirects, or unknown toolbars have appeared
• Security software has been disabled or is generating alerts it did not raise before
• Network activity spikes during off hours with no clear cause
• Unfamiliar applications or processes are visible in the task manager

What to do immediately

1. Disconnect the infected device from the network immediately
2. Run reputable anti-malware tools to identify and remove threats
3. Remove any unauthorized or unrecognized applications
4. Reset all credentials that were used on the infected device
5. Monitor remaining systems for signs that the infection has spread

Signs you may be affected

• Devices are running unusually slowly, overheating, or behaving erratically
• Unexpected pop-ups, browser redirects, or unknown toolbars have appeared
• Security software has been disabled or is generating alerts it did not raise before
• Network activity spikes during off hours with no clear cause
• Unfamiliar applications or processes are visible in the task manager

INCIDENT TYPE 06

Cloud Account Compromise

Attackers have gained access to your cloud environment. This may have happened through exposed API keys, misconfigured storage, or access permissions that were broader than they needed to be. Many cloud compromises do not require sophisticated techniques. They take advantage of configuration gaps that accumulate over time and go unreviewed.

As more business operations move to cloud infrastructure, these incidents are becoming more common. The absence of visible disruption makes them particularly difficult to detect.

Signs you may be affected

• Unexpected billing spikes or resource usage appear with no corresponding project activity
• Unfamiliar storage buckets, compute instances, or user accounts appear in your cloud environment
• API keys or service account credentials have been found in public repositories or logs
• Access logs show activity from unusual geographic locations
• Data stored in cloud buckets is found to be publicly accessible

What to do immediately

1. Revoke all exposed credentials and API keys immediately
2. Audit access permissions and review all recent activity logs in detail
3. Secure any misconfigured storage buckets or publicly exposed resources
4. Rotate all API keys and service account credentials across your environment
5. Assess the full scope of data that may have been accessed or copied

How to prevent this

• Enforce strong identity and access management practices from the outset
• Use role-based access controls and avoid blanket administrator permissions
• Monitor cloud environments continuously with automated alerting for anomalies
• Run automated configuration checks to catch drift before it becomes a vulnerability
• Apply zero trust principles: verify every access request rather than assuming it is legitimate.
  

Preparation is what separates a contained incident from a prolonged crisis.

The steps in this guide are more effective when they are planned in advance rather than worked out under pressure. Knowing who to call, what to isolate, and what to preserve makes a material difference in how quickly your business recovers.

At LENET, we work with organizations to build security postures that reduce both the likelihood and the impact of these incidents. That includes incident response planning, access controls, staff training, and ongoing monitoring.

If you would like to understand where your current gaps are, a cybersecurity audit is the clearest place to start.

Book a free consultation with LENET today for a comprehensive cybersecurity audit and ensure your business is prepared to respond decisively when it matters most.