Top 10 Hacker Attacks on Servers and Effective Ways to Protect Them

Every day, thousands of attacks on servers take place around the world: some target large banks and government agencies, others target small online stores and blogs. Many website owners believe that hackers are only interested in “big fish” and do not pay enough attention to protection. This is a mistake. A hacker attack on a server can result in the loss of customer data, hours of downtime, and a blow to reputation from which a business may struggle to recover.

This article is written for a broad audience: whether you run a company, maintain a blog, work as a system administrator, or simply want to understand how digital security works, you will find clear explanations here without unnecessary jargon. We will examine the ten most common types of attacks, show how they work in practice, and explain what actually helps protect against them.

What is a server attack and why is it important to know about it

A server is a computer that is constantly connected to the internet and performs a task: stores files, processes website requests, sends email, manages a database. Precisely because a server is always “online,” it becomes a target. A hacker attack on a server is a deliberate action aimed at disrupting its operation, stealing data, gaining unauthorized access, or using the machine’s resources for malicious purposes.

Types of server attacks are usually divided by goal and method. Some attacks aim to “take down” a service, others to quietly get inside and lie low, and still others to steal specific data. Understanding these differences helps you choose the right defense strategy: there is no universal “shield,” and what protects against one threat may be powerless against another.

10 most common hacker attacks on servers

1. DDoS attack — artificial paralysis

What is a DDoS attack on a server? The abbreviation DDoS stands for Distributed Denial of Service. Imagine a store that is suddenly flooded by thousands of people who do not intend to buy anything: they just stand there, block the aisles, and prevent real customers from entering. That is exactly how DDoS works: attackers send a huge stream of fake requests to a server from hundreds of thousands of devices (a so-called botnet) until it stops responding to legitimate requests.

A type of attack that overloads a server can take different forms: network-level flooding (when the server is overwhelmed with data packets), application-layer attacks (simulating real users’ requests to a website), or so-called amplification attacks, when the attacker causes third-party servers to repeatedly “reflect” and multiply traffic. DDoS attacks do not steal data directly — they create downtime that costs the company money and reputation. That is why they are often used as a distraction while another group of attackers quietly infiltrates the system.

2. SQL injection — hacking through the search field

Most websites work with a database: they store logins, passwords, orders, and personal data there. Queries to this database are written in SQL. SQL injection is a technique in which the attacker enters a piece of code instead of ordinary data directly into a website form: a search field, login form, or comment box. If developers have not implemented protection, the server will interpret the malicious code as a legitimate request and execute it.

The consequences can be catastrophic: an attack on a web server through SQL can give the hacker a full dump of the database — that is, all users’ logins, passwords, and card data at once. This is how millions of accounts on major platforms were compromised in the past. According to OWASP (Open Web Application Security Project), SQL injections have consistently been among the top three most critical web vulnerabilities for more than ten years.

3. XSS — injecting a script into a page

Cross-Site Scripting (XSS) works differently: here the code is injected not into a database, but directly into the HTML page seen by another user. Suppose a site allows comments and does not filter their content. Instead of a comment, the attacker writes JavaScript code. When the next visitor opens the page, the browser executes that code: steals session cookies, redirects to a phishing site, or records keystrokes.

XSS is especially dangerous for high-traffic services: one malicious script can “process” thousands of unsuspecting users in just a few hours.

4. Brute force — password guessing

One of the oldest and still effective methods. The idea is simple: a program automatically tries possible passwords — from the simplest (“123456,” “password”) to complex combinations — until it finds the right one. Modern tools can check billions of combinations per second, especially if the attacker knows the target’s login or email address.

Brute-force attacks are not aimed only at websites. SSH ports, admin panels, email accounts, and corporate VPNs are also targeted. According to the Verizon Data Breach Investigations Report, weak or stolen credentials are involved in most successful breaches.

5. Man-in-the-Middle — interception in transit

A man-in-the-middle (MitM) attack is the interception of data exchange between two parties. Imagine that you hand a letter to a courier, and he reads it, sometimes changes the contents, and sends it on — neither sender nor recipient knows about it. Technically, such an attack is possible on open Wi-Fi networks, through ARP table spoofing in a local network, through compromise of intermediate routing nodes, or through SSL stripping — downgrading a secure connection to an insecure one.

6. DNS server attacks — route poisoning

DNS is essentially the internet’s “phone book”: it translates human-readable website addresses (for example, example.com) into numeric IP addresses by which a server can be found. DNS server attacks come in several varieties. The most common is DNS spoofing, or cache poisoning: the attacker replaces the record in the DNS table so that when a user types the address of the real site, they end up on a fake one. This is an excellent way to carry out mass phishing: victims notice nothing because they see the correct address in the browser.

Another variant is DNS amplification: a technique in which DNS servers are used as traffic amplifiers in a large-scale DDoS attack. The attacker sends a small request, and in response the server sends the target a huge stream of data.

7. Exploits and zero-day vulnerabilities

A “zero-day” is a vulnerability in software that developers do not yet know about, or have just learned about, but for which a patch has not yet been released. Attackers who find such a hole can exploit it until the vendor closes the gap. Attacks of this type are the most valuable on the cybercrime market: the cost of a good zero-day exploit for popular enterprise software can reach millions of dollars.

8. Bot attack and credential stuffing

A bot attack on a server is an automated attack using bot programs. One of the most common scenarios is credential stuffing: attackers take a database from leaks of other services (the logins and passwords of millions of people have long been sold on private forums) and automatically test these combinations on other websites. Since many people use the same passwords everywhere, this attack is often highly successful.

9. RCE — remote code execution

Remote Code Execution (RCE) is every hacker’s dream: a vulnerability that allows arbitrary code to be executed directly on a remote server. If an attacker achieves RCE, they effectively gain full control over the machine: they can install programs, read files, create users, and set up hidden access. RCE arises because of errors in application code, outdated libraries, or improper handling of incoming data.

10. Supply chain attack

This method has become especially relevant after several high-profile incidents in recent years. Instead of attacking a well-protected target directly, attackers compromise the software vendor or third-party service that the target trusts. A compromised update or library reaches thousands of clients at once. A notable example is the SolarWinds attack in 2020, which affected hundreds of companies and government agencies around the world through a network software update.

Comparative table of attacks: type, target, and protection methods

How a company server attack unfolds in practice

Let us examine the mechanics using DDoS as an example, so it becomes clearer what this is all about. The attacker first creates a botnet — a network of thousands of infected computers, smartphones, and smart devices (routers, surveillance cameras, and even televisions). The owners of these devices usually have no idea that their equipment is taking part in the attack: the malicious program runs in the background. On command, all these devices begin sending requests to the target server at the same time. Several tens of thousands of requests per second — and a normal server stops coping. For an outsider, it looks simple: the site is “down” or opens with a huge delay.

Understanding how a given attack works technically is important first and foremost for defense. Many people are interested in the question of how to carry out an attack on a server, and the internet does indeed discuss this openly. This is no coincidence: security specialists, penetration testers, and students in related fields study attack methods precisely in order to build proper defenses. Knowing the mechanics of an attack means understanding exactly what kind of protection needs to be put in place against it.

Effective protection methods: what actually works

Network filtering and Anti-DDoS

Protection against DDoS begins at the network level. Specialized services analyze incoming traffic in real time, filter out anomalous flows, and allow only legitimate requests through. Many VPS server providers offer built-in DDoS protection as part of their infrastructure solutions — this is especially relevant for companies that are just deploying their server environment and do not want to build protection from scratch.

Using a CDN (content delivery network) also helps: traffic is distributed among several geographically separated nodes, and one stream of requests can no longer “take down” the entire infrastructure. Rate limiting — limiting the number of requests from a single IP address per unit of time — blocks most simple application-layer attacks.

Web Application Firewall (WAF)

A WAF (Web Application Firewall) is a filter that sits between the user and your website. Unlike a regular network firewall, which simply allows or blocks traffic by IP addresses and ports, a WAF “reads” the contents of each incoming HTTP request. If SQL code is sent into a search field instead of text, or if a login form receives hundreds of login attempts per second, such requests are blocked before they even reach the application or database. For a public web service, this is one of the most important layers of protection: it blocks SQL injection, XSS, brute force, and API attacks without requiring manual configuration for each threat. Serverspace WAF works together with a CDN and can be activated from the control panel in just a couple of clicks — without additional software or complex configuration.

The principle of least privilege and segmentation

One of the fundamental principles of security is this: every component of the system should have exactly as many permissions as it needs to function — and not a byte more. If the web server is compromised, it should not have access to a database with banking data. If one virtual machine is infected, it should not “see” its neighbors. Network segmentation and proper access control significantly limit the spread of an attack within the infrastructure.

Two-factor authentication and password management

Most successful breaches begin with stolen or weak credentials. Two-factor authentication (2FA) — when, in addition to a password, you must confirm the login by a second method, such as a code from an app — drastically reduces the risk. Even if a password is leaked, the attacker will not be able to log in without the second factor. This is one of the cheapest and at the same time one of the most effective protection measures.

Timely updates and patch management

Most successful attacks exploit vulnerabilities for which a patch has long since been released — nobody just bothered to install it. Regularly updating the operating system, web server, CMS, and all libraries in use closes the vast majority of known attack vectors. This requires discipline, but not budget.

Practical scenarios: who gets attacked and how

Scenario 1: an online store during a sale. A competitor or “customer” organizes a DDoS attack on the server on peak days — for example, during Black Friday. The site is unavailable for several hours, and the store loses revenue and customers. Protection: provider-level anti-DDoS, CDN, and advance rate limiting setup.

Scenario 2: a small blog or news portal. An outdated version of WordPress with an unpatched plugin becomes a target for automated scanners. Through the vulnerability, the attacker gains remote code execution (RCE) and installs a cryptocurrency miner on the server. The site owner notices this only weeks later because of the increased hosting bill. Protection: automatic updates, WAF, load monitoring.

Scenario 3: a corporate server with SSH access. A system administrator has configured SSH on the default port and has not limited login attempts. Bots try passwords around the clock. If the password is weak or has been used on another breached service, access will be gained. Protection: change the port, disable password login (keys only), fail2ban or similar.

Scenario 4: attacks on company servers through third-party services. A company uses a cloud CRM, and the developer of that CRM becomes the target of a supply chain attack. A malicious update reaches thousands of clients. Protection: minimum permissions for integrations, monitoring of anomalous activity, backups.

Scenario 5: a phishing attack followed by MitM. An employee connects to the corporate VPN through a compromised Wi-Fi access point in a café. The attacker intercepts session data. Protection: using a VPN with strong encryption, configuring HSTS on the site, employee training.

Typical mistakes in server protection and how to avoid them

The first and most common mistake is believing that “we won’t be hacked, we are too small.” Automated scanners and bots attack all IP addresses indiscriminately. Company size does not matter: if there is an unpatched vulnerability on the server, it will be found and used.

The second mistake is postponing updates. “I’ll install it next week” turns into “never.” Updates should be applied immediately after release or according to a pre-approved schedule. Automatic security updates are a good solution for most components.

The third mistake is having a single point of failure in monitoring. If no one watches server logs and no alerts are configured for anomalous activity, an attack can develop for weeks before it is noticed. Intrusion detection systems (IDS/IPS) and centralized log collection are an essential part of the infrastructure.

The fourth mistake is ignoring backups. Backups do not protect against a breach, but they do make recovery possible afterward. Backups should be stored separately from the main server, in an isolated environment: otherwise, in a ransomware attack, you will lose both the data and the backups.

The fifth mistake is leaving administrative interfaces open. Control panels for databases, monitoring tools, phpMyAdmin and similar services should not be directly accessible from the internet. Only through VPN, an IP allowlist, or at least with additional HTTP authentication.

DoS and DDoS: what is the difference and why it matters

A DoS attack on a server (Denial of Service) differs from DDoS in that it comes from a single source: one computer sends a stream of requests to the victim. Today, this method is practically ineffective against normally configured infrastructure — blocking one IP is very easy. That is why attackers switched to distributed attacks, which is where the D in DDoS comes from. Traffic comes from tens of thousands of different addresses belonging to infected devices around the world, and blocking them all without harming legitimate users is much more difficult.

Understanding this difference is important when choosing protection: a solution designed only for IP blocking is of little help against a full-scale DDoS attack on a server. You need tools capable of analyzing behavioral patterns and recognizing anomalous traffic regardless of its source.

Infrastructure as part of a security strategy

Server security begins with choosing a reliable platform. Companies that rent virtual servers from large providers receive a number of basic protective measures as part of the package: physical data center security, network filtering, and, as a rule, the ability to add additional tools — firewall, DDoS protection, and backups. For example, when renting VPS servers at Serverspace, network security tools and ready-made infrastructure are available, which removes some of the basic risks. This does not replace proper configuration of the server and applications themselves, but it creates a solid foundation.

The main rule is this: security is not a product that can be bought once. It is a continuous process: monitoring, updates, audits, penetration testing, staff training. Attacks on company servers are becoming more sophisticated, and the only way to stay ahead is to regularly review and strengthen protection.

Where to start right now

The threats are real, but most of them are preventable. Server attacks — from massive DDoS to targeted SQL injections — work according to predictable patterns, and for each of them there are proven countermeasures. The most important thing is not to postpone protection “until later.”

If you are just starting to build the security of your infrastructure, begin with the basics: install all available updates, enable two-factor authentication on all administrative accounts, close unused ports, set up regular backups, and make sure your provider offers at least basic DDoS protection. These steps do not require large budgets, but they close the vast majority of attack vectors from which a hacker attack on a server begins in real life.

The next level is WAF, IDS/IPS, regular code audits, pentests, and bug bounty programs. But even without them, a basic level of security hygiene makes you a significantly harder target than the vast majority of servers on the network.

FAQ — frequently asked questions

What is a DDoS attack on a server in simple terms?

It is the deliberate overload of a server with a huge number of fake requests arriving simultaneously from thousands of different devices. As a result, the server cannot process real user requests and becomes unavailable — roughly like a phone line that is being jammed by thousands of spammers at once.

What does a DDoS attack on a server mean for an ordinary user?

For an ordinary website visitor, it looks simple: the site does not open or loads very slowly. User data is usually not stolen in this case — DDoS is aimed at unavailability, not theft. However, if the attack serves as cover for another attack, the risks increase.

How can I tell that my server is under attack?

Key signs: a sharp unexplained increase in traffic, server slowdown or unavailability, suspicious log entries (login attempts from many different IPs, unusual database queries), anomalous CPU or network load. A monitoring system with configured alerts will let you know about the attack in time.

Is it possible to fully protect against hacker attacks?

Absolute protection does not exist — that is the honest answer. The goal is not to make hacking impossible, but to make it too expensive and difficult for the attacker. A properly designed multi-layered defense turns your server from an “easy target” into a “not worth the effort” category for most attackers.

How dangerous are DNS server attacks for an ordinary user?

Very dangerous, because they are invisible. The user sees the correct site address in the browser, but ends up on a fake page. There they enter a login and password — and the data goes to the attacker. User-side protection: use a reliable DNS resolver (for example, one with DNSSEC support), pay attention to the HTTPS certificate, and do not ignore browser security warnings.

What is a bot attack and how is it different from a regular hack?

A bot attack is an automated attack using software without human involvement. Bots can guess passwords, scan a site for vulnerabilities, mass-create fake accounts, or imitate user behavior. What distinguishes them from a “manual” hack is scale and speed: a bot does in a second what would take a person hours.

Does a small website need to think about server security?

Yes, and this is not an exaggeration. Automated scanners roam the entire internet looking for vulnerable machines — they do not distinguish between large corporations and personal blogs. A compromised server of a small site can be used to send spam, mine cryptocurrency, or serve as a node in a botnet for attacks on other victims. Basic protection takes little time, but it saves you from serious problems.