In your experience, what were some unconventional signs that there's a malware inside your network?

Even though I've applied many security rules on my network, I'm constantly worried there's some hidden, sleepy trojan on my corporate network waiting to be activated.

What I've applied til now is this:

- Only few countries are whitelisted to send incoming emails. All other countries are blocked

- Only allow doc, pdf, excel, png, jpg attachments. All other attachments are blocked.

- Macro scanning and File Analysis of mail attachments.

- All USB ports are blocked (as storage)

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