Dangerous antivirus programs: which ones to avoid and how to protect your PC

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Connecting to the internet today without at least some protection is almost like leaving your front door wide open. The web is teeming with malware, scams, and attacks that only need a moment's inattention to infiltrate your computer, steal your data, or even render it unusable. Windows 10 and Windows 11 include their own security engine, Microsoft Defender, which provides a reasonable foundation, but many users choose to install third-party solutions, believing this will make them much more secure.

The problem is that not all antivirus programs are equally effective, reliable, or honest . Some fall short in detecting threats, others are overly paranoid, generating numerous false positives, and some are simply malicious programs masquerading as security tools. In this article, we'll review which antivirus programs are truly dangerous (due to weakness or being fraudulent), what labs like AV-Comparatives and AV-Test say, what types of malware exist, and how to protect your PC from the most common traps.

Weak antivirus programs full of false positives: the ones to avoid

Independent testing is the most reliable way to determine which antivirus programs perform well and which fall short. Laboratories like AV-Comparatives (Austria) and AV-Test (Germany) subject leading security suites to real-world scenarios: malicious websites, zero-day threats, known malware, resource consumption, and performance in the face of false positives.

Although almost all detection engines today use the cloud to share signatures and analyses, each manufacturer implements its own engine and databases . This is reflected in detection rates and, above all, in the number of legitimate files that are mistakenly flagged as malware. The combination of these two factors results in some names that, based on the data, are best left undetected.

According to recent results from AV-Comparatives, Quick Heal is one of the clearest examples of an antivirus that falls short . In their real-world protection tests, this software was only able to block around 94,2% of threats. In other words, it missed approximately 5,8% of malware. For a product that's supposed to be your last line of defense, that's a significant shortcoming.

Another striking case is Panda Security, which for years was a leading security provider in Spain . In the tests analyzed, Panda detected approximately 97,4% of the samples, but in return, it generated a very high volume of false positives compared to its competitors. Many users nostalgically remember it from the Windows 98 era, but since the major detection and mass deletion failure it suffered in 2009 with Windows XP, it has not managed to recover its reputation in the most demanding tests.

There's also the case of Malwarebytes as a primary antivirus . Its detection rate is around 98,1%, but it suffers from a disproportionate number of false positives. As a complete antivirus solution, it's not the ideal option; however, it makes perfect sense as a secondary option for on-demand scans, since its anti-malware engine often detects residual threats that other products miss.

In the middle tier are names like K7 and Trend Micro . Their pure detection rates are quite high (99,3% and 99,5%), but their problem lies elsewhere: the number of false positives . When an antivirus flags everything as malicious , the risk is no longer so much the actual malware itself, but rather that it will end up blocking programs you need, drivers, system libraries, or your own documents.

Why false positives are also dangerous

It might seem that an antivirus that detects "too much" is better than one that falls short, but an excess of false positives can cause more problems than it solves . A false positive is basically when the antivirus decides that a completely legitimate file, application, or website is a threat.

When this happens occasionally it's just a nuisance, but if the engine makes mistakes repeatedly, very serious situations can arise : blocking of work programs, inability to install critical software, wasted time checking for false alerts, and, in extreme cases, deletion of vital system files.

There have been documented incidents where some antivirus programs have quarantined DLL libraries belonging to both legitimate applications and Windows itself . The result is that certain programs suddenly stop opening, or the system begins to malfunction to the point of failing to boot. Recovering a computer in this state may require complete system restores or even a clean reinstall.

That's why labs like AV-Comparatives and AV-Test place such importance on the balance between detection and false positives . It's not just about stopping all malware, but about doing so without breaking the system or impacting user productivity. Their methodology is transparent, audited (in the case of AV-Comparatives, with ISO 9001 certification), and widely recognized by the industry.

It's important to clarify that editorial reviews of certain products are based on objective data , not personal biases. A poor performance from an antivirus program in a report doesn't mean it's useless; it simply means that, compared to competitors in the same tests, it has shown more limitations: lower detection rates or too many false positives.

Antivirus programs that fail in security: the case of Bkav and others

Looking at the AV-Test results, we find another name that raises concerns: Bkav . This antivirus entered the market selling itself as a pioneering solution based on Artificial Intelligence, capable of inspecting everything that enters and leaves the computer to predictively stop threats.

On paper, Bkav promises multi-layered protection for networks, operating systems, and data against classic malware, ransomware, miners, keyloggers, adware, and other similar threats. The problem is that, when tested in a lab, the results don't live up to the hype.

In a recent report, Bkav was the only antivirus program to "fail" AV-Test's tests . It scored 3 out of 6 in both protection and usability, indicating that something is amiss. Looking at the numbers, its engine only detected around 88,5% of threats, while the average for the other programs comfortably exceeded 97,5%.

In addition to all this, Bkav generated five times more false positives than the average of its rivals . In other words, it neither detects malware well nor fully respects legitimate files. For now, it's a product best avoided if you want to trust your security software, although we'll have to see if future versions improve.

Along with Bkav, AV-Test also identifies eScan, K7 Security, and AhnLab as less than ideal options , as they don't achieve the highest possible protection score. This doesn't mean they're completely vulnerable, but given the availability of free and paid alternatives that receive perfect scores, there's little point in taking the risk.

Fake antivirus: when the threat disguises itself as protection

Besides weak antivirus programs, there's another, even more worrying front: that of "antivirus" that is actually malware . This type of software is known as rogue antivirus or fake antivirus software, and it's expressly designed to deceive the user.

The scam typically works in a very similar way: the victim visits a website or opens a file that triggers a fake security alert on the screen, claiming that the computer is riddled with infections. From there, the program offers to "fix" the problem in exchange for installing a supposed tool or paying for a license.

In many cases, the goal is to scare people enough to get them to pay for something they don't need , or that doesn't even work. In others, in addition to the financial scam, the fake software itself installs the real malware: Trojans, spyware, ransomware, or backdoors to remotely control the computer.

To minimize the risk of encountering this type of malicious "protection," security experts like those at Kaspersky recommend following some basic guidelines:

• Keep your operating system and applications up to dateAlways install the security patches Windows, the browser, the PDF reader, plugins like Flash (if you still use them) and any other program susceptible to attack.
• Update your legitimate antivirus software frequently. And, if you can, enable automatic updates so that the signatures are downloaded automatically.
• Be wary of certain search engine resultsespecially from sponsored links that promise to miraculously "clean your PC" or "speed it up".
• Enter the manufacturer's website address yourself. in the browser bar, instead of coming from banners or dubious links.
• Don't open attachments you weren't expecting., even if they appear to come from a known contact, without first checking with that person if they actually sent them to you.
• Think twice before clicking on links in emails, messages, or social media.especially if they promise you gifts, "cracked" downloads, or eye-catching content.

The most destructive viruses in history: the real impact of malware

To understand why choosing the right antivirus software and keeping your system up to date is so important, one only needs to look at the history of major malware outbreaks . In recent decades, viruses and worms have cost billions of dollars and brought down entire networks of businesses and public organizations.

One of the most devastating cases was Mydoom , considered the most expensive malware outbreak to date. In 2004, it caused damages estimated at around $38.000 billion (more than $52.000 billion adjusted for inflation). Technically, it was a worm that spread via mass email; at one point, it accounted for 25% of all emails circulating on the internet.

Mydoom extracted email addresses from infected computers, automatically forwarded them to those contacts, and turned them into part of a botnet used to launch distributed denial-of-service (DDoS) attacks . Despite an official reward of $250.000, its creator was never publicly identified. And most disturbingly, it still appears in phishing campaigns today, generating approximately 1% of that malicious traffic worldwide.

Another legendary worm was Sobig , from 2003, which is estimated to have caused around $30.000 billion in damages. It appeared in several variants (A through F) and disguised itself as legitimate software in email attachments . It managed to crash systems at airlines like Air Canada and disrupt operations across all kinds of industries.

Klez , for its part, infected around 7,2% of all computers worldwide in 2001 (approximately 7 million machines). It sent emails impersonating known senders, attempted to disable other installed viruses, and evolved into increasingly aggressive variants. It remained active for years, demonstrating how difficult it is to completely eradicate certain malware.

The name most people probably remember is ILOVEYOU . It spread in 2000 with a devastating social engineering trick: it posed as a love letter in a supposed text file. When opened, it was automatically forwarded to all the user's contacts. Within days, it compromised more than 10 million computers. Its creator, the Filipino Onel de Guzman, was not convicted because his country did not yet have specific cybercrime laws.

More recently, WannaCry was the ransomware that brought data encryption to the forefront of the media. In 2017, it spread in a matter of hours across 150 countries, infecting some 200.000 computers and paralyzing hospitals, businesses, and government agencies. The attack was only stopped when a British researcher accidentally discovered an "emergency switch" in the code . Most of the affected computers had outdated operating systems, a lesson that experts continue to emphasize today.

Another key name is Zeus , which emerged in 2007 as a financial theft platform. It was behind approximately 44% of banking malware attacks and infiltrated 88% of Fortune 500 companies, as well as some 2.500 organizations in nearly 200 countries. It operated as a botnet dedicated to capturing banking credentials and emptying accounts . More than 100 members of the network were arrested in 2010, but some of its code remains active in current Trojans.

Nor should we forget worms like Code Red , first detected in 2001, which infected nearly a million systems in just a few hours. It lived exclusively in RAM, making it harder to locate, and launched DDoS attacks, including one against the White House website. Or SQL Slammer , from 2003, which overwhelmed the internet by randomly selecting IP addresses, exploiting vulnerabilities, and replicating at a brutal speed, taking down ATMs and banking services.

In 2013, CryptoLocker showed the world just how profitable the classic ransomware model could be: encrypt files, display a ransom note with a countdown timer, and demand payment. It affected more than 250.000 computers and used the Gameover Zeus botnet for its mass distribution. Its formula remains the basis for many modern ransomware attacks targeting businesses.

And as a curious aside, the Sasser worm , written by a 17-year-old German student, locked millions of computers in 2004 by exploiting operating system vulnerabilities without the user having to click anything. The young man was arrested after being denounced by an acquaintance seeking the reward offered for his capture.

Other malware that marked an era and the evolution of threats

Beyond that "top 10," there are several names that give a clear idea of ​​how malware has evolved. Conficker , for example, appeared in 2009 and still infects older or poorly managed computers today. If it were to become active on a large scale again, it could have a considerable impact.

Stuxnet was malware's leap into the geopolitical arena. Designed to sabotage Iran's nuclear centrifuges, it demonstrated that malicious software could be used as a physical weapon against industrial infrastructure . It wasn't targeting home users, but rather very specific control systems (SCADA).

In 1999, Melissa was one of the first mass-mail viruses to demonstrate its potential for widespread propagation. The FBI estimated the damage at around $80 million. It was relatively simple, but it overwhelmed email servers around the world.

In 2007, Storm Worm spread through emails containing purported news about storms and extreme weather events. It was one of the first major examples of social engineering adapted to current headlines , something that remains prevalent today with emails impersonating official agencies, banks, or courier companies.

Today, the landscape has changed: threats are more targeted, stealthy, and focused on financial gain . Double-extortion ransomware, supply chain attacks, advanced banking trojans, and malware that attempts to hide in firmware or beneath the operating system are now commonplace in cybersecurity.

Difference between a virus, a worm, and ransomware

Although we often use them interchangeably, viruses, worms, and ransomware are not exactly the same thing . Understanding the difference helps in better interpreting news about cyberattacks.

Strictly speaking, a computer virus needs a host file to run . It is usually embedded in executables, documents, or macros. When the user opens that file, the virus activates, replicates to other files, and can modify, delete, or steal information, as well as serve as an entry point for more malware.

A computer worm is autonomous: it requires no action from the user other than having a vulnerable system. It exploits flaws in the operating system or applications to infiltrate the network, replicate itself, and spread. This is precisely why they are so dangerous in corporate environments: a single unpatched computer can compromise an entire network.

Ransomware is more than just a method of propagation; it's a specific type of malware defined by its objective: it encrypts files or blocks system access and demands payment in exchange for the decryption key . In some countries , it's known as "data kidnapping." It can be delivered via a Trojan horse, a worm, a website exploit, or a phishing email.

Most of the major historical "viruses" on the list are actually worms, and today ransomware is the most costly threat to businesses and governments . It typically combines automatic propagation, data encryption, prior theft of sensitive information, and public blackmail.

Real-life case: What happens if only one VirusTotal engine detects a threat?

Situations like this are becoming increasingly common: you download a file from a "grey" source (for example, a game DLC activator) , upload it to VirusTotal, and see that only 1 out of 60 engines flags it as a Trojan. In a similar example, Jiangmin antivirus flagged an executable used to activate DLCs for The Sims 4, while the other engines flagged it as clean.

In such cases, it's tempting to think it's just a false positive and move on . And it might be, but it's also true that many cracks, activators, and license bypass tools are among cybercriminals' favorite infection vectors. They target people predisposed to let their guard down in exchange for something "free."

The wisest course of action when a single engine flags a suspicious file is to combine several factors : the file's reputation (time in circulation, number of users who have submitted it), its digital signature (if present), the history of the distributing website, and, above all, common sense. If the file intends to modify game or system components and doesn't come from the official store, the risk is already high.

While technical analysis might sometimes involve examining hashes, sandbox behavior, or heuristics, the sensible approach for the average user is simply not to run it . Losing a "free" mod or DLC is infinitely better than accidentally installing a Trojan that steals your banking credentials or encrypts all your documents.

The most dangerous types of malware and how they work

Beyond the specific names, it's important to understand which malware families are most common and what they're looking for . This helps identify suspicious behavior at a glance.

A classic computer virus focuses on spreading and causing damage to files and systems. It can corrupt documents, sabotage programs, or open backdoors for other attacks. It often relies on Office macros, executables, or removable media.

Ransomware , as already mentioned, encrypts the contents of your computer (or an entire network) and displays a ransom note. Some variants only affect certain types of files, while others affect the entire system. In recent years, the double extortion model has become popular: in addition to encrypting files, they steal data and threaten to publish it if payment is not made.

Computer worms focus on moving across networks at high speed , exploiting vulnerabilities. Once inside, they can do anything from deleting data to integrating the computer into a botnet dedicated to launching DDoS attacks, mining cryptocurrencies, or sending spam.

Trojans disguise themselves as legitimate software : cracks, installers for popular programs, supposed updates, etc. They don't replicate on their own; they require you to run them. From there, they can steal data, allow remote control of your computer, download more malware, or spy on your activities.

Adware displays unwanted ads in your browser or on your system itself , often in the form of pop-ups or toolbars you haven't asked for. Beyond being annoying, some forms of adware track your activity and collect personal data without your permission.

Spyware silently spies on you ( how to remove spyware ): it captures keystrokes, takes screenshots, logs websites visited, and sends that information to a remote server. It can sneak in as part of another program, exploit security vulnerabilities, or trick you through phishing.

Botnets are networks of infected devices controlled by an attacker . Each of these devices (bots) can be your PC, your router, or even an IoT device. When coordinated, they can be used to launch massive attacks, distribute malware, or conduct large-scale spam campaigns.

Keyloggers are a specific type of spyware that records everything you type on your keyboard. They can have legitimate uses (parental controls, monitoring in businesses) when installed properly and under regulation, but in the hands of criminals they are an ideal tool for stealing passwords, banking information, or private conversations.

Symptoms that your computer may be infected

Although many current threats try to go unnoticed, there are typical signs that can alert you that something strange is happening on your PC:

• System much slower than usual without a clear cause.
• Programs that open or close on their own, or constant crashes.
• The appearance of icons, shortcuts, or files that you don't remember installing.
• Pop-up ads even when you're not browsing.
• Changes to the browser's homepage or default search engine without your permission.
• Strange error messages when starting or shutting down the computer.

In Windows 10 and 11, you can check your protection status from "Windows Security ." Simply type that term into the Start menu search bar and go to "Virus & threat protection" to see when the last scan was performed and if there are any active alerts ( find out if my PC has a virus ).

Best practices to protect yourself from dangerous antivirus software and malware

Beyond choosing a reliable antivirus, most of your defense depends on your habits . A prudent user with a decent antivirus is usually better protected than a careless user with the best suite on the market.

Some basic tips that are always worth applying are:

• Install a good antivirus and keep it updatedMicrosoft Defender is a solid and free foundation; other highly rated options in AV-Comparatives and AV-Test include Avast Free, Kaspersky, McAfee, or Bitdefender, depending on the type of license you want.
• Do not open emails or attachments from unknown senders. And be wary of files you weren't expecting, even if they appear to be from someone you know.
• Activate a pop-up blocker and review your browser's privacy settings.to limit tracking and reduce exposure to dubious websites.
• Keep Windows and other programs up to date with Windows Update and your own update systemsMost successful attacks exploit vulnerabilities that already have patches.
• Verify that User Account Control (UAC) is enabledso that you always have to authorize major changes to the system.
• In Windows 10 and 11, verify that "Tamper Protection" is turned on.to prevent malware from disabling your antivirus or changing security settings behind your back.
• Avoid installing pirated software, cracks, and activatorsbecause they are one of the most commonly used vectors for sneaking in Trojans, keyloggers, and ransomware.

In some professional environments, it also makes sense to add layers of protection at the hardware or firmware level , such as the technologies integrated into some equipment from manufacturers like HP (for example, HP Wolf Security). These types of solutions aim to detect and contain attacks even if the operating system has already been compromised.

If you add to all this the use of strong and unique passwords, two-step authentication when possible, and some common sense while browsing , you will greatly reduce the likelihood of ending up in the hands of dangerous antivirus programs, banking malware, or massive ransomware campaigns.

Choosing the right antivirus, keeping up with updates, and applying a few simple habits when browsing and managing your files makes a huge difference: most of the biggest malware disasters in history exploited outdated systems and unsuspecting users —precisely the mistakes you can easily avoid today if you know which products not to use, why to distrust certain "antivirus" programs, and how to recognize the symptoms of an infection in time.