A known malicious program or connection
What happened
A program known to be used in attacks ran, or the PC connected to an address known to be used by attackers.
How serious
Serious: deal with it today.
Steps: Windows PC
Take the PC off the network now: unplug the cable and turn off Wi-Fi. Don't switch it off: what's in memory helps your IT provider.
Ask the person at that PC what they were doing at that time (installing something, a link in an email, a USB stick).
Run a deep scan: Windows Security → Virus & threat protection → Scan options → Microsoft Defender Antivirus (offline scan) → Scan now. The PC restarts.
Change the passwords used on that PC (Windows, Microsoft 365 or Google, banking) from ANOTHER, clean device.
How to check it’s fixed
Fixed when the deep scan finds nothing, protection is on again and Ojava shows the PC as healthy for 24 hours.
When to call your IT provider
Call your IT provider today, before using the PC again for work.