How Cybercriminals Attack Your Network: 9 Methods Explained

By now you probably understand how much damage a cybercriminal can do to your finances, your customer base, your reputation, and ultimately your business. But the question I get most often from Houston business owners is the practical one: how do they actually break in? There are literally dozens of ways a hacker can get into your system, and most of them don’t look dangerous until it’s too late.

This post is adapted from Chapter 5 of my book, Protecting Your Business Against Hackers. If you’d rather read the whole thing, you can download the full book here. Below are several of today’s most common methods criminals use to wreak havoc on an entire network, explained in plain English so you can recognize them before they cost you.

The 9 Most Common Ways Hackers Get In

Most attacks aren’t some Hollywood scene of a hooded genius cracking your firewall. They’re quiet, ordinary-looking, and they usually walk in through your inbox. Here’s what to watch for.

Spamming

A lot of people assume “spam” is an acronym. It isn’t: the name actually comes from an old Monty Python sketch where the word gets repeated over and over until it’s both annoying and meaningless. That’s a perfect description of the flood of useless, uninvited emails landing in your inbox every day.

Spam is still the number one entry point into a network, for one simple reason: people click links they shouldn’t. It also clogs things up, burying the important business and personal messages you actually need. A few years ago spam was easy to spot thanks to broken English and obviously fake links. Today’s scammers are smarter: they use real company logos and spell-check everything so it slips past you. Accidentally clicking a spam link can invite malware straight into your computers and network. Don’t wait for it to cause a problem; get proactive with spam-detection software and anti-spam filters that keep it out of the inbox in the first place.

Phishing

Most people can spot a junk email at a glance. Phishing is much harder, because it uses realistic, professional-looking emails designed to trick you into handing over passwords and other sensitive information.

Criminals who run phishing campaigns constantly perfect their craft to mimic a company you trust. One widespread example impersonated Visa, telling recipients their credit card would be disabled unless they visited a website and changed their password immediately. Every step, from the email to the fake site, matched Visa’s branding. Another common version is a “bank” email pressuring an employee into sharing company banking details. These messages often feel urgent and threatening on purpose, because a rushed person is a careless person. Some even carry attached zip files that unleash viruses the moment they’re opened. Rather than risk the embarrassment of asking the boss whether an email is real, employees often just act on it, and it takes only seconds to let a hacker in.

Malware

Malware is a mash-up of “malicious” and “software”: any program or code built to damage devices or steal data. It’s the umbrella term that covers viruses, worms, spyware, ransomware, Trojans, and more.

Why do criminals pour so much effort into making it? Money, mostly: they sell it online to the highest bidder for other criminals to use. Some deploy malware as a form of protest, some to test security, and some governments even use it as a weapon of cyber war. Malware can also quietly turn one of your computers into a “bot” that attacks other machines. That’s an important point: even if your firewall blocks traffic from countries like China or Russia, it won’t stop a malware attack launched from a computer already inside your own office.

Ransomware

Ransomware is exactly what it sounds like: software that holds your computer system and sensitive information hostage until you pay for the decryption key. Picture walking into the office and finding you can’t open a single customer file, your financials, or the R&D records for your next product launch. Criminals know how much that information is worth to you, which is precisely why they bet you’ll pay.

It usually enters through one employee opening something they shouldn’t. It’s commonly hidden in innocent-looking attachments, an “unpaid invoice” PDF or a package-tracking Word document, and once it runs, you can’t open anything else until the ransom is paid. Newer “ransomworms” like WannaCry and NotPetya made this even worse. The threat is real at every scale: in August 2019 a coordinated attack hijacked the networks of twenty-two Texas towns, and a year earlier Atlanta spent upward of $18 million recovering from a ransomware infection (they chose not to pay). Nearly half of all ransomware attacks target health care, where thousands of patient records make a payday irresistible. And while the headlines focus on big organizations and city governments, attackers also cast wide nets across small businesses: infect enough of them, and even a small percentage paying is a win for the criminal.

Spyware

Spyware is another type of malware, downloaded just as easily as ransomware through the same unassuming email attachments. The difference is it doesn’t appear to do anything at all. Behind the scenes, it’s busy: logging every keystroke across your company or quietly copying emails and shipping all of it back to whoever planted it.

The only hint you might notice is that your system feels a little slower than usual. Spyware often runs alongside adware to monitor your internet and social media habits, but make no mistake: it’s a serious privacy and security threat that can harvest personal information for identity theft and fraud. Since you have zero control over what it watches or where the data goes, the only real answer is to prevent it up front and remove it the moment it appears.

Adware

Most people recognize adware the second they see it: those annoying pop-ups crowding your screen. Adware (“advertising” plus “malware”) is less outright dangerous than other threats and more just irritating. That said, it can still undermine your security settings, track your activity, and drag down your computer’s performance.

Adware exists mainly for pinpoint marketing. Where spyware watches your browsing habits, adware serves up ads based on what you’re searching for. Think of your grandmother’s old party line, where you could overhear the neighbors: you ask the operator for Pizza Hut’s number, and before you can dial, Domino’s calls with a special. The advertiser knows what you want and gets in front of you to push the sale.

Worms

Worms are unusual in the malware world because they’re “stand-alone”: they don’t need anyone to interact with them to spread. Once a worm gains access to a network, often through an innocent-looking email attachment, it spreads on its own by exploiting technical vulnerabilities.

An internet worm is a lot like a parasite. Like a tapeworm, it duplicates itself across as many computers as it can reach. Worms themselves are rarely destructive, but here’s the catch: they frequently create backdoors in your system, open doors a hacker can later use to launch far more serious malware attacks.

Trojan Viruses

You know the story of the Trojan Horse: the Greeks built a giant wooden horse, hid soldiers inside, and the people of Troy rolled it right through their own gates, losing the war before they realized what hit them. A Trojan virus works the same way, hiding inside a program that looks completely harmless.

Unlike viruses and worms, which self-replicate across files and machines, a Trojan’s job is to smuggle dangerous malware onto your computer or network. These advanced threats survive by going unnoticed, and while they sit there quietly they can collect information, punch holes in your security, or take over your computer and lock you out entirely.

As people get better at spotting malware, criminals get more sophisticated about tricking them into clicking. Social engineering is similar to phishing but far more personal. It can be as simple as posing as a coworker in a legitimate-looking email asking for a password, or as elaborate as building a relationship online or in person, scanning someone’s social media to learn where they hang out, and targeting them outside of work.

Ransomware and other malware can sneak in by exploiting technical vulnerabilities, but the simplest way to spread it is to get someone to open the front door for you. That’s exactly what happens when a hacker outsmarts an employee into opening an email that looks like it came from a friend or colleague. The more advanced the social engineering, the more likely someone unknowingly invites the attacker right into your business.

Frequently Asked Questions

What is the most common way hackers get into a business network?

Spam and phishing emails. Spam remains the number one entry point simply because people click links they shouldn’t, and phishing is dangerous because the emails look legitimate, often mimicking a trusted brand or a company executive. The overwhelming majority of attacks start with a single person clicking something in their inbox, which is why employee awareness matters as much as any software.

What’s the difference between malware, ransomware, and a virus?

Malware is the umbrella term for any malicious software: it includes viruses, worms, spyware, ransomware, and Trojans. A virus is one type of malware that replicates and infects files. Ransomware is a specific type that locks up your files and demands payment for the key to unlock them. They’re related, but they behave differently and call for layered defenses rather than a single tool.

How does ransomware usually get into a company?

Almost always through one employee opening an attachment they shouldn’t. It hides in innocent-looking files like a fake “unpaid invoice” PDF or a package-tracking document. Once it runs, it locks you out of your own files until a ransom is paid, which is why email filtering, reliable backups, and employee training are your best protection.

Can my firewall stop all of these attacks?

No. A firewall is important, but it can’t stop a threat that an employee invites in by clicking a link or opening an attachment, and it won’t block malware attacks launched from a computer already inside your network. Real protection is layered: combining filtering, monitoring, endpoint security, backups, and trained employees working together.

Know Your Weak Spots Before a Hacker Does

Cybercriminals today have an entire arsenal aimed at every computer in your company. From simple phishing, spyware, and adware to dangerous malware, costly ransomware, and Trojans, an unprepared business is a sitting duck. The good news is that every one of these methods has a defense, and most of them come down to the same handful of layered protections plus a team that knows what to watch for.

I’ve been protecting Houston businesses since 2002, and I work with companies in the 10–200 employee range that don’t have a corporate IT department to fight off these threats. That’s exactly the gap we fill. If you want to know which of these doors are open in your own network, let’s talk.

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