Master AOL: what it is and how to remove it

It depends on where the file is and who signed it, not on the name. Open Task Manager, go to the Details tab, right-click diag.exe and choose Open file location. A file inside Program Files or System32 with a valid digital signature from a known company is usually part of a legitimate program.

A file in AppData, Temp or ProgramData with no signature, especially one that restarts itself after you end it, is suspicious. If you cannot tie the process to anything you installed, uninstall recent unfamiliar programs and run a Microsoft Defender Offline scan.

Ending an unknown process is safe in the sense that Windows will warn you before you close anything critical, and a restart brings back whatever Windows needs. Ending diag.exe will not remove it, though: if a task or startup entry launches it, it returns at the next sign-in.

Use ending the process as a test. If something important stops working, it belonged to a program you use. If nothing changes and it comes back by itself, find and disable its starter, delete the file and scan the PC.

Most security vendors would call it a potentially unwanted program rather than malware. The difference is intent and consent:

• malware hides and harms
• while unwanted programs are installed with a click someone barely noticed
• then do more than expected

The sign reported here, an unfamiliar process called diag.exe in Task Manager, is typical of the second group. In practice the label matters less than the result.

Whatever it is called, a program you did not choose should go, and the place it came from should be checked for other programs. Microsoft Defender can block this class of software if you switch on Potentially unwanted app blocking in Windows Security.

It depends on the program, and no measurements have been published for Master AOL. The sign reported is an unfamiliar process called diag.exe in Task Manager. Check for yourself: open Task Manager, find its process and watch the CPU, memory and network columns for a minute while the PC is otherwise idle.

Steady use with nothing open is a strong reason to remove it. Even if it seems light, it may run more processes under other names, so sort Installed apps by date and remove anything else from the same day. Then restart and compare.

Often yes, if Potentially unwanted app blocking is on. Microsoft Defender detects many bundled and unwanted programs as PUA, but by default it only blocks them during download in some cases. For a program already installed, uninstall it yourself from Installed apps first, then run a full scan in Windows Security to catch leftovers.

If an unfamiliar process called diag.exe in Task Manager returns after that, run the Microsoft Defender offline scan, which works before Windows starts. Switching on the PUA setting afterwards helps keep similar programs out.

Turn on Potentially unwanted app blocking in Windows Security > App & browser control > Reputation-based protection settings, with both Block apps and Block downloads checked. Download programs from the developer's own site or the Microsoft Store, choose Custom in installers and untick extra offers, and treat large download buttons on file sites as ads.

Apps from the Microsoft Store are checked by Microsoft and uninstall cleanly. Keep real-time protection on, so that bundled offers flagged as unwanted are stopped before they install.

There is no report of that. Unwanted programs make money from ads, offers, data about your browsing or the use of your connection, not from stealing passwords, and the sign reported here is an unfamiliar process called diag.exe in Task Manager.

That said, a bundle can contain more than one program, and you cannot be sure what else ran on the day it arrived. After removing Master AOL, run a full scan in Windows Security.

If it finds a password stealer or a trojan, change your passwords from another device. If the scan is clean and you see no unknown sign-ins, there is no need to change them.

Work in three steps. First uninstall it from Settings > Apps > Installed apps, together with anything installed on the same day. Second, remove what restarts it: unknown entries under Settings > Apps > Startup and tasks in Task Scheduler with matching names.

Third, clean the browsers: extensions you did not add and changed search settings. Restart and watch for an unfamiliar process called diag.exe in Task Manager; if it does not come back within a day, the removal is complete.

If it does, run a Microsoft Defender offline scan, which works before Windows starts and finds helpers that hide while the PC runs.

Possibly. Some programs that cause an unfamiliar process called diag.exe in Task Manager are real products from real companies that simply use aggressive distribution. Check the publisher in Installed apps and the digital signature in the file's Properties.

A known publisher and a program you actually use mean you can keep it and only adjust its settings. An unknown publisher, a program you never opened and no clear purpose mean it should go.

If it came bundled with something else, the decision is easy: you did not choose it, so remove it and keep the program you actually wanted.

Fortect scans Windows for malware and unwanted programs and repairs the system files and settings they change, and its free scan shows what it finds on your PC before you decide anything.

For Master AOL, follow the plan above as well: the browser steps take back permissions and settings that no scanner treats as a threat, and uninstalling the program that brought it removes the source.

Run Microsoft Defender's full scan and, if anything was found, its offline scan as a second opinion. If the symptoms are gone after the plan and both scans are clean, there is nothing more to do.