External Hard Drive (Mac) been Scanning 79hrs

[REDACTED]

I had some malware show up on my computer & got rid of it with Avast. (After realizing Avast had got turned off on our computer.) I had never thought about scanning the external hard drive (which we just use for backup). I updated our Avast for Mac and it has been scanning (removable volumes scan) the external hard drive for 79hrs now. Is this normal? I don't want to stop it because it's already found 82 infections on the external drive.

[tumic]

If there are Timemachine backups (or other hard-link based "structures") on the external hard drive,
than the scan can take really long as the disk has "virtually" several times the real capacity
for the scan in this case. In such case it may for example scan 30TB of data (1TB HDD * 30), which
may take dozens of hours.

Another possibility is, the scan has "deadlocked" somewhere, but without more info, it is hard to say.

[.: Mac :.]

As tumic said, likely these are the Time Machine backups. These can contain copies of infected files.  If everything is in good standing with your Mac, and there are no other files on the drive, I would wipe the drive and then let Time Machine create a full backup that you know is clean.