How to deal with unused registered public IP subnets

[Johnny Wong <johnnywkm () gmail com>]

> Hello list,
>
> Recently, in an external assessment effort, we found a list of 
> public IP subnets registered under my company's name. However, about 
> half of them are no longer in use. I could only guessed that they 
> were leftovers from mergers/acquisitions in the past. Being a good 
> Internet citizen, I would release these unused subnets since there's 
> a worldwide shortage of IPv4 addresses. However, bringing this point 
> forward to the management is rather tricky -- because they think 
> these are still company's property, keep for future expansion and so on.
>
> There are possibilities that these unused IP subnets/addresses being 
> used for malicious intent (spyware, scam, trojan propagation, 
> spoofing). What other risks are there with us retaining these IP 
> subnets/addresses?
>
> What do other companies do with unused IP subnets/addresses? Do they 
> just release them or keep them for future needs?
>
> Thank you,
>
> JW