What is an infostealer?
Infostealers are lightweight malware that silently extract passwords, session cookies, authentication tokens, autofill data, cryptocurrency wallets, and other sensitive information, then exfiltrate them to an attacker-controlled server. They are highly successful because most infections are self-inflicted, coming from users who intentionally execute fake installers, fake captcha prompts, cracked/pirated software, game mods, or "free" software that provide a pathway for the compromise to execute. Once executed, the malware exfiltrates everything instantly, leaving almost no artifacts for antivirus tools to detect. The reason is that they use native OS components and common tools built into each platform, such as PowerShell on Windows, bash, terminal, and osascript on macOS, along with curl on both platforms to collect and siphon credentials. These actions appear as normal user or system activity to virus/malware scanners both during and after execution. So don't bother wasting time on virus/malware scans, as they will likely find nothing.
What is compromised?
Infostealers mainly focus on two things. The first is exfiltrating session cookies and authenticated tokens from the device they run on. The second is decrypting encrypted databases that contain passwords and other sensitive information from various locations. Both types of information are sent to a remote attacker‑controlled server. Whether you are on macOS or Windows, the first step always succeeds because it requires no user input and happens very quickly, so there is nothing a user can do to stop it. If your device is a Mac, the behavior is different due to macOS native protection. While session cookie exfiltration is successful on macOS, the malware needs the Mac user password for other things like decrypting password databases, crypto wallets, and similar items, so it will prompt you to enter your password. If you do not provide the password, the malware cannot steal your passwords or other sensitive data protected by the password. Aside from this, the infostealer also siphons out crypto wallet keys, TOTP seeds, API keys, SSH keys, and many other items, including installing background services. The last one listed requires doing a clean reinstall of the OS.
How to recover?
The recovery steps depend on the type of device the compromise was executed on. If the device is Windows, unfortunately both session cookies and all passwords, crypto wallet keys, and similar data are exfiltrated successfully. However, if the device is a Mac and you did not provide your password when prompted, you only need to recover from stolen session cookies. On the other hand, if you did provide your Mac password, the compromise is identical to Windows. I have dissected several variants of infostealers and found that architecturally they are identical in how they operate, so the steps below apply to any variant. Follow the steps in the exact order specified to effectively recover from an infostealer compromise.
1. Revoke active sessions: This is the most critical step that most people miss. Unlike what many armchair experts advise on infostealer compromise, you should not waste time trying to find a clean device for this step. Just do it right on the compromised device without disconnecting from the internet as soon as you realize you are a victim of an infostealer. The reason I recommend using the same device is because not all online services provide a way to log out from all devices, and your main goal is to revoke the stolen session cookies, not the session cookies on other devices that are not stolen and are perfectly fine. If a service does not provide a logout‑from‑all‑devices option, your attacker will keep access to that service for a long time until the stolen session cookie naturally expires, which can take hours, days, or even weeks. So it is very important to use the same compromised device for this step. The actual step to revoke the session is simply logging out from every service on that device, which makes the stolen session cookies useless to the attacker. Do not do anything else on that device. Once you have logged out of all services, turn off the compromised device.
2. Change password: This step must be done using a device that is not compromised, or on your compromised device if you have already reinstalled the OS as described in step 4 below. Login to each of your online accounts and change your password or optionally change to a passphrase. Enable 2FA if not enabled already, preferably an authenticator app or hardware key-based method rather than SMS. Make sure there are no email forwarding rules in your email accounts. Setup a recovery email if there is not one already and finally, regenerate the backup codes.
3. Backup: Backup your documents, photos, and other data. Infostealers cannot damage them and do not even target that type of content. They are perfectly fine to backup and restore after the next step. You only need to worry about your primary drive where the operating system resides. Your external drives are fine because infostealers do not interact with them as far as I know.
4. Reinstall OS: If your compromised device is a PC, create a bootable media. It can be a USB stick or secondary SSD with an installable OS obtained directly from Microsoft. Now go to your compromised device BIOS settings and enable booting from the alternate drive, the USB or secondary SSD, and choose to do a complete wipe and reinstall of Windows on your primary SSD or hard drive. For a Mac, boot into recovery mode, choose Disk Utility, and select the top-level internal disk to erase. Follow that by selecting reinstall macOS. If you are unsure how to do this, there are plenty of tutorials on YouTube you can follow to accomplish this step.
5. Browser Extensions: This would be a good time to review all your browser extensions, delete the ones you do not use, and validate the ones you use regularly. Most people have no idea how much access they grant to browser extensions or how dangerous they can be. I highly recommend reading this blog that explains the details. https://blog.selvansoft.com/2026/05/browser-extensions.html
6. Safety Tips: Follow as many online safety tips as possible from the blog link below. The more of them you follow, the stronger your online safety becomes. https://blog.selvansoft.com/2025/01/online-safety-tips.html
7. Monitor: Monitor your credit cards, online banking, and similar financial accounts. Optionally, I recommend freezing your credit following this guide: https://blog.selvansoft.com/2023/05/howto-credit-freeze.html
8. Advice: Stay away from installing stuff from random websites. You can assume all free/pirated software has some form of malware. There is no such thing as a safe website to download free stuff. It just does not exist, regardless of what you heard or what your buddy online told you about a software from a site being safe.
