Common Types of Cyberattacks: The Complete 2026 Guide

Ransomware

Ransomware is malware that encrypts an organization's files and demands payment for the decryption key. It is the attack category that generates the largest average financial losses and the most board-level attention. In 2026, ransomware groups have moved well beyond simple encryption. Modern ransomware attacks follow a double-extortion model: attackers first steal data, then encrypt it, then demand payment both for the decryption key and for the promise not to publish the stolen data. This means paying the ransom does not guarantee recovery — and many organizations that pay still find their data published.

Ransomware groups operate as businesses. They maintain affiliate programs, customer service portals for negotiating payments, and reputation systems that encourage victims to pay because attackers who consistently provide working decryption keys generate more revenue. The most active groups in 2026 — LockBit, BlackCat, and Clop — specifically target organizations with cyber insurance, because insured organizations have demonstrated ability and willingness to pay.

Phishing and Spear Phishing

Phishing is the use of deceptive communications — email, SMS, voice calls, social media messages — to trick recipients into revealing credentials, clicking malicious links, or transferring funds. It remains the most common initial access vector for cyberattacks because it targets human behavior rather than technical vulnerabilities, and human behavior is harder to patch than software.

Spear phishing is targeted phishing — attacks crafted specifically for a named individual using personal information gathered from LinkedIn, breach databases, company websites, and social media. A spear phishing email to a CFO that references a recent acquisition, uses the correct internal terminology, and appears to come from the CEO's email address is not a generic scam. It is a precision social engineering instrument. AI-generated phishing content has significantly raised the quality bar — grammatical errors and awkward phrasing, once reliable indicators of phishing, are no longer reliable signals.

Adversary-in-the-Middle (AiTM) Attacks

AiTM attacks are the evolution of traditional phishing that makes MFA irrelevant. The attacker places a proxy between the victim and a legitimate authentication service. The victim enters their credentials and approves their MFA prompt — against a site that looks exactly like Microsoft, Okta, or Google. The attacker captures the authenticated session token in real time. MFA was completed correctly, but the attacker now has the post-authentication proof that grants access to the application.

AiTM is the dominant credential attack technique in 2026 because it defeats the control that most organizations deployed specifically to stop credential theft. Platforms like Evilginx2 make AiTM attacks accessible to moderately skilled attackers. Only FIDO2 phishing-resistant MFA has the cryptographic binding that defeats AiTM — TOTP codes and push notifications do not.

Social Engineering and Vishing

Social engineering is the use of psychological manipulation to trick people into taking security-damaging actions. Vishing — voice phishing — is its most effective current form. Scattered Spider's breach of MGM Resorts began with a LinkedIn search and a 10-minute phone call to the MGM help desk. The attacker impersonated an IT administrator, provided information gathered from breach databases, and successfully obtained an MFA reset. The $100M breach cost was preceded by a phone call.

AI voice cloning has made vishing substantially more dangerous. An attacker can now call a help desk using a convincing synthetic replica of a specific employee's voice, trained on 30 seconds of source audio available from LinkedIn videos or company webinars. Help desk staff who rely on recognizing familiar voices as a vishing defense no longer have a reliable detection heuristic.

Supply Chain Attacks

Supply chain attacks compromise organizations not directly but through the software, services, or vendors they trust. The SolarWinds attack compromised 18,000+ organizations by inserting malicious code into a legitimate software update. The MOVEit breach in 2023 compromised hundreds of organizations simultaneously through a zero-day in file transfer software they all used. The Okta support environment breach in 2023 gave attackers visibility into customer identity configurations through a trusted vendor's systems.

Supply chain attacks are disproportionately effective because they leverage established trust. Security controls that would block an unknown file or an unfamiliar domain do not block a digitally signed software update from a trusted vendor. The risk question for every organization is not just how secure their own systems are — it is how secure every software vendor, SaaS platform, and managed service provider in their supply chain is.

Credential Stuffing

Credential stuffing uses username and password combinations leaked in previous data breaches to attempt authentication on other services. The attack exploits password reuse — the common human behavior of using the same password across multiple accounts. Breach databases containing billions of credential pairs are freely available on criminal markets. Automated tools submit these credentials against login pages at scale, identifying valid combinations that work because the user reused a password from a previously breached service.

Organizations that believe their employees do not reuse passwords are almost always wrong. Password reuse is the default human behavior. Enterprise password managers enforced through policy are the control that eliminates this attack class.

Insider Threats

Insider threats are security incidents caused by individuals with authorized access — employees, contractors, former employees with active credentials, and third-party vendors with system access. They range from deliberate data theft by employees planning to join a competitor, to negligent exposure of sensitive data through misconfiguration, to malicious sabotage by disgruntled employees.

Insider threats are particularly dangerous in M&A contexts. Employees who learn about an acquisition may exfiltrate data before the deal closes. Former employees whose accounts are not properly deprovisioned may retain access to sensitive systems months after departure. Third-party vendors whose access was provisioned for a specific project and never revoked represent an ongoing exposure that is rarely tracked systematically.

Zero-Day Exploits

Zero-day exploits target vulnerabilities that have not yet been patched — often because they have not yet been discovered or publicly disclosed. Nation-state actors maintain stockpiles of zero-day vulnerabilities for use in high-value operations. Criminal groups purchase zero-days on exploit markets for targeted campaigns. April 2026's Patch Tuesday included two actively exploited zero-days, one in Windows Defender and one in SharePoint, both of which were already being used against organizations before the patch was available.

The zero-day window — the period between exploitation beginning and a patch being available — is not a period where organizations are helpless. Defense-in-depth controls, behavioral detection, network segmentation, and privileged access restrictions all limit the damage a zero-day can cause even when it cannot be blocked outright.

DDoS, Business Email Compromise, and Emerging Attack Types

Distributed Denial of Service (DDoS)

DDoS attacks flood a target's infrastructure with traffic to make services unavailable. For most PE portfolio companies, DDoS is a lower financial risk than ransomware or data theft — but it becomes material when availability is core to the business model. Financial services firms, e-commerce platforms, and SaaS companies whose revenue depends on uptime face significant financial exposure from extended DDoS events. DDoS-for-hire services make the attack accessible to attackers without technical sophistication.

Business Email Compromise (BEC)

BEC attacks use compromised or impersonated executive email accounts to redirect financial transfers. An attacker who gains access to a CFO's email — through phishing, credential theft, or AiTM — can instruct finance staff to redirect wire transfers to attacker-controlled accounts. BEC losses exceeded $2.9 billion in 2023 per the FBI's IC3 report. The technique requires no malware, no ransomware, and no technical sophistication beyond email access — making it one of the highest-ROI attack classes available to financially motivated threat actors.

What PE Operating Partners Need to Know

The attack types described here are not equally likely for every organization. Risk profile varies by sector, size, technology stack, and geographic presence. A healthcare company faces higher ransomware risk due to the urgency of system availability. A financial services firm faces elevated BEC and credential theft risk due to the direct financial transfer opportunities. A manufacturing company with OT systems faces a different threat profile than a pure SaaS business.

Effective security investment starts with an accurate threat model — understanding which attack types are most likely to target your organization based on its specific characteristics. Organizations that deploy controls against the average threat landscape rather than their specific threat profile systematically underprice the risks that are most likely to materialize and overprice those that are not.

Cloudskope's Cyber Risk Assessments begin with a threat modeling exercise that maps your organization's specific profile — sector, size, geography, technology, data, and business relationships — against the threat actors and techniques most likely to target organizations like yours. Security investment follows the threat model, not the vendor's sales cycle.