If you suspect or know that you’re already infected with a virus on your Windows 10 computer, what do you do? Follow these steps and you may be able to get back to work as soon as possible.

You should already know: use antivirus software. These programs – from free tools and paid antivirus software to major security suites – keep tabs on your Windows computer with scans, real-time monitoring, and even heuristic analysis of files and processes so that new ones can be identified threats. It is imperative, especially with Windows, to have antivirus installed.

However, even the best antivirus is not 100% infallible. A device already compromised by malware could enter your network, people can personally place malware on a system, and some malware remains inactive, waiting to attack. Social engineering and phishing schemes can trick people (you) into clicking or downloading an infected link or attachment. Hell, there are even scareware programs that don’t seem to be antivirus or antispyware, but when you install them, you get infected! Always download from source – avoid third-party download sites.

Sometimes it’s hard to tell when you’ve been hit by a computer virus. There are a lot of signs that you should watch out for – incredibly slow performance in which, once the computer has shut down, browser pop-ups when no browser is open, scary warnings from security programs that don’t you have even installed redemption requests. If you suspect or know for sure that you have a malware infection, here are the steps you need to take to remove the malware immediately.

Update your antivirus

First, make sure your antivirus software is completely up to date with the latest virus definitions – this is how you identify malware, based on what came before. Antivirus vendors are constantly updating these lists as they encounter new viruses and Trojans in the wild and in the lab. If your software is obsolete one day, you risk an infection.

Return, restart, scan and scan again

If you have set system restore points in Windows when malware attacks and cannot be fixed, take advantage of this opportunity to reset your system. The trick might be done … but probably not. The malware may be too smart.

You can restart directly on the built-in Microsoft Defender that comes with Windows 10. To do this, go to Settings> Update and Security> Windows Security> Virus and Threat Protection. (If you’re running a third-party antivirus, you’ll see it here, plus an option to enable Microsoft Defender for “periodic scans” that won’t interfere with the real-time activity of the installed antivirus.)

Once Windows Defender is enabled even for periodic scans, look for Scan Options. Click it and check the box next to Microsoft Defender Offline Scan. After a reboot, it will take about 15 minutes to scan for “very persistent rootkits and other malware,” according to Microsoft.

Scan offline Microsoft Defender

If you have a remote access Trojan (also known as a RAT) on your computer, someone may be accessing your computer remotely. This is bad news. Also, if you’ve caught some ransomware, you don’t want it to encrypt files that you automatically back up to the cloud. Take a deep breath and get off the internet. Pull Ethernet off your computer, turn off Wi-Fi, unplug your router if you’re right. Ensures that the PC is disconnected. Make sure you are not using Wi-Fi from a neighbor or a nearby company to stay online on the side. Then try a few antivirus scans. If Windows is compromised beyond use – it may not even allow you to log in – switch around the operating system by starting directly in the antivirus software. Use a bootable program, sometimes called a “Live CD” or “Save CD” – although nowadays you will usually boot from a USB drive. To be safe, set it up now while your computer is healthy.