Email remains one of the most effective attack vectors because it reaches employees directly and relies on human judgment rather than technical barriers. With billions of messages exchanged daily, attackers have endless opportunities to embed malicious attachments, craft convincing phishing links, or disguise social engineering ploys as routine correspondence.

Damage control after an incident is important, but the greatest protection comes from spotting threats before a single click is made. This guide highlights eight types of email attacks every employee should be able to recognize right from business email compromise schemes that exploit authority and urgency to vendor impersonation tactics that slip past traditional filters.

Understanding these threats equips you to treat your inbox as the frontline of defense. Recognizing warning signs early turns what could be a costly breach into an avoided incident.

Email remains the most common entry point for cybercriminals because it bypasses perimeter defenses and exploits human judgment. A single message can deliver malicious links, weaponized attachments, or carefully crafted social engineering, turning ordinary communication into a doorway for malware, credential theft, or financial fraud.

Attackers favor email for its reach and efficiency. One campaign can target thousands of employees at once, while automated tools tailor each message to mimic legitimate correspondence. Unlike hardened systems, inboxes rely on individual decision-making; one click is often enough for compromise.

Email also exposes multiple attack surfaces at once. Links may redirect to cloned login pages, attachments can conceal harmful code, and persuasive requests manipulate trust. This combination makes the inbox the earliest and often most decisive battleground for stopping an attack before it escalates across the organization.

Email threats have grown increasingly sophisticated, often blending seamlessly with routine business communication. Generative AI enables attackers to craft messages with flawless grammar and polished corporate tone, making them indistinguishable from legitimate correspondence. Clone-phishing kits replicate logos, layouts, and even error messages from trusted sites, while domains that differ by a single character appear authentic at first glance.

Visual deception is reinforced by technical tactics. Man-in-the-middle proxy pages capture credentials and intercept MFA codes in real time. Compromised employee or vendor accounts distribute emails that pass SPF, DKIM, and DMARC checks, allowing fraudulent requests to appear as standard invoices, HR updates, or project notifications.

Because these tactics integrate so naturally into daily workflows, detection is far more challenging. Recognizing how these threats operate is critical, ensuring employees remain cautious even when a message looks routine. Awareness paired with strong verification processes is the first defense.

BEC is one of the most financially damaging forms of cybercrime because it relies on trust. Attackers impersonate executives, vendors, or colleagues to insert themselves into legitimate business processes and trick employees into transferring money or sharing sensitive information. Unlike technical exploits, BEC attacks succeed through social manipulation and carefully crafted communication.

Common scenarios include a “CEO” demanding an urgent wire transfer, a “vendor” submitting revised payment details, or an “HR colleague” requesting payroll changes. Attackers often use AI-generated language, spoofed domains, or compromised accounts to make messages indistinguishable from authentic correspondence. The combination of authority, urgency, and familiarity creates strong pressure to act quickly and skip regular checks.

Warning signs include high-value financial requests that bypass approval processes, email addresses with subtle alterations, and instructions to keep the transaction confidential. The safest response is to pause, verify the request through trusted communication channels, and follow established approval workflows. Simple verification steps prevent funds from being diverted and stop BEC scams before they succeed.

Credential phishing works by replicating trusted login portals so convincingly that employees hand over usernames, passwords, and even MFA codes without hesitation. Defense depends on slowing down, inspecting details carefully, and avoiding login links delivered through email.

Attackers copy HTML, CSS, and images from real websites to build near-perfect replicas, then host them on look-alike domains such as micr0soft-signin.com. Many display valid HTTPS certificates, exploiting the false belief that the padlock guarantees safety. Some campaigns embed QR codes to trick mobile users, while others use man-in-the-middle proxies to relay sessions to real services, capturing credentials and authentication codes in real time. Even polished replicas reveal flaws: grammar errors, unusual requests for additional details, or login prompts that appear at odd times.

• Inspect the entire URL and confirm certificate details.

• Access key services only through bookmarks or by typing addresses directly.

• Treat unexpected login prompts or unrequested MFA codes as suspicious and alert security immediately.

Employees should consistently follow these practices to keep even the most convincing clones from succeeding.

Attackers often disguise malware inside files that appear routine, making every attachment a potential risk. Office documents with macros are widespread, prompting users to “enable content” and executing hidden code when activated. PDFs with embedded scripts, executables masked with double extensions, or files compressed in archives pose similar dangers. Another rising technique, HTML smuggling, assembles malicious payloads directly in the browser to evade email filters.

Safe handling requires discipline. Always open attachments in protected view, never enable active content without verification, and route suspicious files through endpoint scanners or cloud sandboxes. Confirm unexpected attachments through separate channels, such as a direct call to the sender, rather than replying to the email. These steps build multiple layers of defense while preserving productivity.

Once an account is compromised, attackers operate as trusted insiders. They add forwarding rules, register rogue devices, and escalate privileges, often blending into normal communication patterns. Because these attacks leverage valid identities, they bypass traditional perimeter defenses.

Early warning signs include unexpected MFA prompts, logins from unfamiliar devices or locations, new inbox rules that conceal alerts, and changes to recovery emails or authorized applications. Compromised accounts are quickly weaponized to phish colleagues, steal data, and expand access.

Swift action is essential when signs of compromise appear. Even a single anomaly should prompt immediate investigation and a password reset. The sooner detection happens, the less chance attackers have to move laterally or escalate privileges.

Fraudulent invoices and altered payment instructions frequently arrive through compromised vendor accounts. Attackers monitor threads and wait for payment discussions, then reply with updated bank details that appear authentic. Because the messages originate from legitimate domains, they pass standard authentication checks and blend into normal correspondence.

Defenses require process, not just technology. Confirm any change in payment instructions directly with the partner using trusted phone numbers. Scrutinize sender and reply-to addresses for subtle inconsistencies, and enforce finance procedures that mandate secondary authorization for account changes. These human verification steps, paired with technical safeguards, close the gap that attackers exploit in vendor impersonation schemes.

Urgent request scams manipulate trust in authority and pressure targets into acting quickly. Attackers pose as executives or legal counsel, framing demands as confidential and time-sensitive to discourage verification. The combination of authority and urgency suppresses critical thinking and compels compliance.

A typical example involves an email from a supposed CEO directing an immediate wire transfer under strict secrecy. In that moment, the instinct to obey overrides normal validation steps, which is precisely what scammers intend.

The best defense is deliberate verification. Call the requester using a trusted number, compare sender details carefully, and remember that legitimate business rarely demands immediate action outside established procedures. Even a short pause restores judgment and breaks the manipulative spell.

Attackers frequently hide malware in files that look ordinary, turning common attachments into potential entry points. Office documents with macros remain a favored method, prompting users to “enable content” that silently executes hidden code. PDFs with embedded scripts, executables disguised with double extensions, and compressed archives present similar risks. An increasingly common tactic, known as HTML smuggling, delivers malicious payloads directly within a browser session to bypass email filters.

Reducing this risk requires careful handling. Open attachments in protected view and avoid enabling active content unless the source is confirmed. Run suspicious files through endpoint scanners or sandbox environments before opening them fully. When an unexpected attachment arrives, confirm its legitimacy through a trusted communication channel such as a direct call, rather than replying to the same email thread. Following these practices creates multiple layers of defense while allowing employees to work productively without unnecessary disruption.

Attackers often exploit trusted vendor accounts to send fraudulent invoices or malware that bypasses authentication checks. Because messages come from legitimate domains, they appear routine and slip through traditional filters unnoticed.

When attackers gain control of a supplier’s mailbox, they can observe conversations and insert themselves at key moments, such as payment discussions. An altered invoice with swapped account details looks authentic and is often approved without question, since technical checks confirm it originated from the real domain.

Mitigation requires both process and intelligence. Vendor callbacks ensure payment changes are verified through trusted channels, while behavioral profiling highlights anomalies such as altered payment instructions or unusual communication patterns. Together, these measures close gaps that standard gateways fail to catch.

Modern email threats are crafted to slip past traditional filters and even well-trained employees. Social engineering, account takeovers, and vendor fraud exploit trust in ways that signature-based tools cannot reliably stop. This is where Abnormal adds an essential layer of protection.

The platform uses behavioral AI to learn how every employee and vendor typically communicates, who they interact with, when, and in what context. Any deviation, such as a sudden change in payment details or suspicious login activity tied to unusual file sharing, is flagged immediately. Protection extends across email, Slack, and Teams, ensuring threats are caught wherever collaboration happens.

Vendor Compromise Protection and Account Takeover Detection provide focused safeguards, while the behavioral engine identifies zero-day BEC, clone phishing, and urgent request scams. Employees remain the first line of defense, and Abnormal supplies the safety net that keeps mistakes from becoming breaches. See how this works in practice with Abnormal’s demo.