When malware enters a network using an encrypted session, what does the IDS see in the payload?

As long as the IDS has been updated with the signature for the specific piece of malware, the IDS will recognize the malware.

The IDS only needs to recognize a unique artifact, which is a snippet or subroutine of malicious code, in order to alarm on the malware.

The IDS will only see an encrypted payload, and will be unable to identify the malware, even if the malware matches an IDS signature.

If the IDS recognizes the source IP address as malicious, it will flag the encrypted payload for advanced inspection where the malware will be discovered.