Most popular website attacks — what they are, how attackers generally operate, and how to defend
Below is a concise, security-focused guide to the most common web‑site attacks today. I’ll describe what each attack is, the typical attacker methods at a high level (no exploit code or step‑by‑step instructions), signs you’ve been targeted, and practical mitigations you can implement.
1. SQL Injection (SQLi)
What it is: Attacker supplies malicious input that manipulates database queries (e.g., to read, change or delete data).
Typical methods (high-level): Injecting specially crafted input into form fields, query strings, or cookies so server-side SQL concatenation executes unexpected logic. Attackers probe with benign tests, then escalate to extract data or escalate privileges.
Indicators: Unexpected database errors in logs; unusual data access patterns; large volumes of queries from a single IP; dumped data appearing on pages.
Mitigations: Use parameterized queries / prepared statements, input validation, least-privilege DB accounts, ORMs safely configured, web application firewall (WAF), and strong logging/monitoring.
2. Cross‑Site Scripting (XSS)
What it is: Attacker injects malicious client‑side scripts into pages viewed by other users (steal cookies, act as user, deface, etc.). Types: reflected, stored (persistent), and DOM‑based.
Typical methods: Submitting script-like input into comment boxes, search fields, or any place where user input is re-displayed without proper encoding. Stored XSS is particularly damaging because it persists.
Indicators: Users report unexpected popups or redirects; security scanners flag script content in pages; abnormal requests for sensitive actions originating from users’ sessions.
Mitigations: Output‑encode/escape all user data for the context (HTML, JS, URL), use Content Security Policy (CSP), sanitize input server-side, use frameworks that auto-escape, and adopt secure cookie flags (HttpOnly).
3. Cross‑Site Request Forgery (CSRF)
What it is: Attacker tricks an authenticated user’s browser into submitting unintended requests (e.g., change password, transfer funds).
Typical methods: Luring a logged-in user to a crafted link or page that triggers requests to the target site where the user is authenticated.
Indicators: Privileged actions executed without explicit user intent; missing or invalid CSRF tokens in requests.
Mitigations: Use anti‑CSRF tokens for state‑changing requests, require same‑site cookies (SameSite attribute), verify origin/referrer headers when appropriate, and enforce re‑authentication for sensitive operations.
4. Broken Authentication & Session Management
What it is: Weak auth implementation lets attackers impersonate users or hijack sessions.
Typical methods: Credential stuffing (using leaked passwords), brute force, session fixation, session ID theft via XSS or network sniffing.
Indicators: Repeated login failures, logins from unusual locations/devices, sudden increase in account takeover reports.
Mitigations: Rate limit and lockout suspicious login attempts, implement MFA, enforce strong password policies, rotate and expire sessions, secure cookies (Secure, HttpOnly, SameSite), use CAPTCHAs judiciously.
5. Remote Code Execution (RCE) & Command Injection
What it is: Attacker causes the server to execute arbitrary code or OS commands. This is high‑impact.
Typical methods: Exploiting vulnerable components that evaluate user input (unsafely constructed shell commands, unsafe deserialization, vulnerable plugins).
Indicators: New processes or network connections from web servers, unusual outbound traffic, integrity changes to files.
Mitigations: Avoid executing user input, validate input strictly, run services with minimal privileges, use containerization / application isolation, keep software up to date, and use runtime protection/monitoring.
6. File Upload Vulnerabilities & Path Traversal
What it is: Upload allows attacker to place malicious files on server or access files outside intended directories.
Typical methods: Uploading web shells, scripts, or using ../ sequences to traverse directories if path validation is missing.
Indicators: Unexpected files in upload directories, suspicious file types executed, 404s for sensitive files followed by access.
Mitigations: Validate file type and size, store uploads outside web root or serve via unique generated names, normalize and sanitize file paths, scan uploaded files, and restrict execution permissions.
7. Insecure Deserialization
What it is: Deserializing untrusted data lets attackers instantiate objects or execute code.
Typical methods: Sending crafted serialized data to endpoints that deserialize without validation, triggering dangerous behaviors.
Indicators: Unusual exceptions in deserialization code, unexpected object creation patterns, or application crashes.
Mitigations: Avoid deserializing untrusted input; use safe formats (JSON) with whitelisting; apply integrity checks (sign/encrypt serialized blobs) and run deserialization in restricted contexts.
8. Server‑Side Request Forgery (SSRF)
What it is: Attacker forces the server to make HTTP requests to internal systems or external resources on their behalf. This exposes internal services.
Typical methods: Submitting URLs in forms or APIs that the server fetches (image previews, URL validators) to reach internal IPs or metadata endpoints.
Indicators: Web server making requests to internal-only IPs, logs showing outbound requests to cloud metadata services.
Mitigations: Validate and restrict URLs, whitelist allowed hosts, block internal IP ranges, and isolate services that fetch external resources.
9. Denial of Service (DoS) & Distributed DoS (DDoS)
What it is: Overwhelm a site with traffic or resource-heavy requests to make it unavailable.
Typical methods: Botnets or amplified requests; application-level floods exploiting expensive operations (e.g., search with regex).
Indicators: Sudden spike in traffic, resource exhaustion (CPU, memory), high error rates.
Mitigations: Use rate limiting, CDN/edge caching, DDoS protection services, autoscaling, and optimize expensive endpoints.
10. Supply‑Chain / Third‑Party Component Attacks
What it is: Compromise of libraries, plugins, or build tools that your site depends on.
Typical methods: Poisoning package repositories, inserting malicious code into third‑party modules, or compromising CI/CD pipelines.
Indicators: Unexpected changes after dependency updates, alerts from dependency scanners, unusual commits in CI logs.
Mitigations: Pin and audit dependencies, use SBOMs (software bill of materials), scan for known vulnerabilities, sign and verify artifacts, employ least privilege in CI/CD.
11. Phishing & Social Engineering (affecting websites)
What it is: Attackers trick users or staff to disclose credentials or perform actions harming security.
Typical methods: Fake login pages, targeted spear‑phishing to obtain admin credentials, or manipulation of customer service.
Indicators: Credential leaks, suspicious emails, unexpected password resets.
Mitigations: User awareness training, phishing-resistant MFA (FIDO2), strict verification processes for support actions, and email protections (DMARC/DKIM/SPF).
12. Clickjacking
What it is: Attacker embeds a site in a hidden frame to trick users into clicking buttons (e.g., confirm payment).
Typical methods: Overlaying transparent frames or UI elements to capture clicks.
Indicators: Users report odd behavior; site framed in unknown domains.
Mitigations: Use X-Frame-Options or Content-Security-Policy: frame-ancestors to prevent framing.
Detection & Monitoring — how to spot compromise early
- Centralized logging (ELK, Splunk, etc.) with anomaly detection.
- WAF alerts and tuned rules for common attack patterns.
- Rate‑limit and alert on unusual traffic volumes or error spikes.
- Integrity checks (file hashes), endpoint detection, and runtime application self‑protection (RASP).
- Regular vulnerability scanning and penetration testing (ethical, controlled).
Defense-in-Depth checklist (practical, prioritized)
- Keep frameworks, libraries, and servers patched.
- Follow OWASP Top 10 recommendations for secure coding.
- Enforce strong authentication (MFA) and least privilege.
- Use prepared statements / parameterized DB access.
- Escape/encode all output; enable CSP.
- Validate and sanitize user input server-side.
- Store uploads safely; disable executing uploaded files.
- Use WAF, CDN, and DDoS protection for public endpoints.
- Monitor logs, set alerts for anomalies, and practice incident response.
- Audit third‑party dependencies and secure CI/CD pipelines.
Final notes
- Many web compromises result from combinations of small flaws (e.g., XSS enabling CSRF or session theft). Treat security holistically.
- If you manage a site and suspect active compromise, isolate affected systems, preserve logs, and engage incident response or an experienced forensic team.
