avast blocked apt-get upgrade on Kali ,virus alert

i did : apt-get upgrade on on new kali release that is on virtual box (i have win 10 with avast premier)
the a vast blocked 4 times the update telling me he found malware:
we safely abordeted connection on kali.download because it was infected with win32:malware-gen
we safely abordeted connection on kali.download because it was infected with win64:maiware-gen
we safely abordeted connection on kali.download because it was infected with elcar test-not virus!!!
we safely abordeted connection on kali.download because it was infected with win32:malware-gen
more info from one massage:******************
Win32:Malware-gen
http://kali.downlad/kali/pool/main/n..._7.70%2bdfsg1-
5kali1_all.debldate.tar.xzldate.tarl.\user\share\n map\nselib\data\psexec\nmap_service.exe
C:\Program Files\Oracle\VirtualBox\VirtualBox.exe
Web Shield
Connection aborted
****************
does this can be real threats of , false ?
note : virtualbox network setting is NAT.

Long story short, you can whitelist Virtualbox, avast is being overzealous in this case. There are no backdoor running in Kali, so there is nothing to worry about.

Fortinet is known to block tool updates.

Yes, there are some tools that can be classified as malware such as backdoor factory (that can create backdoors) and a few others. If you find that on a end-user systen, yes, there is something to worry about but Kali is a pentesting distro, so this is expected. There are also false positive with tools detected as "Hacktool/NAMEOFTOOL".