While this system of keeping an active list of a company's netblocks works great -- beware. It can suck up memory and result in "cannot allocate memory" errors. Example: building a list for Apple (AS6185) will give you a large list of small netblocks in 17.x.x.x. However, "whois 17.0.0.0" shows that 17.0.0.0/8 is a direct allocation to Apple, so specifying a network alias with a /8 takes a lot less memory. Google is even worse with 7400+ IPv4 netblocks from the whois ASN output.

@Gertjan Thank you. I'll try to find right web-portal to ask my question than. Have asked this on StackOverflow but I am still ignored there ))