Vishu, apologies for the inconvenience of being blocked. Given the way IP addresses are handed out, entire ranges of IPs are often banned.
So, suppose 120.56.138.48 is used to spam
and 120.56.138.137 is used to spam
and 120.56.138.(something else) is used to spam,
That results in many people attempting to fight spam to simply ban the entire range: 120.56.138.*** In your case, this is exactly what happened. Or rather, during the past 1 year, there were 44 separate IP addresses beginning with 120.56.13*.*** that were reported for spam. Apparently, the ISP controlling this range doesn't stop people from engaging in spam using their services. And, that's why they're blocked. I see that, at least for now, you're able to log on with a different IP address. Originally, I was simply going to unblock the range, until I looked at the recent spam reports - that range has been spamming as recently as 4 days ago. So, since you're still able to get on, I'll leave it up to Harvey as to whether there's a way to really narrow down the range. It'd be nice is there was a "between" type of option, but, we only have a wildcard option in this forum software.
So long as your ISPs do not crack down on people using their connections for this purpose, those ISPs will see larger and larger ranges of their IP addresses being blocked at many sites on the Internet. There are, in fact, repositories for people to report the IP addresses that are used for spamming purposes, and people running other sites are able to pre-emptively block those addresses to prevent spam. I don't completely know the nuts and bolts of how the software side works, but our spam filter does exactly that - comparing IP addresses, or registered usernames, or email addresses used for registration - or some combination of these, to flag potential spam before anyone here can see it (other than the mods/admins); and all that does is slows the flow of spam/decrease a little of the moderation efforts to get rid of the spam.
That said, it's worth noting that at one such repository that some of us here use, the first 3 octets of your current IP address have resulted in seven complaints of spamming on other sites.
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