Good luck.
Ok, basically that IP address resolves to the dialup service of a major ISP called Level3. The user is using their dialup service. Quite probably it is a dynamic IP address (meaning it can change every time they log on). 4.240.210.30 is the IP address within an IP range owned by Level3 - 4.0.0.0 - 4.255.255.255. They can doubtless tell who was using that IP address at that time based on their logs anyway. Whether or not they'll take action depends on the ISP!
You can write to them with links to the forum messages stating that:
The poster is in violation [both letter and spirit] of their own AUP (Acceptable Use Policy) at
http://www.level3.net/764.html and request they take action in line with their own AUP.
Mention the messages orginate from an IP address 4.240.210.30 owned by them.
You can use the
abuse@level3.com and also use the hyperlink(s) on that page to use the forms to report it. Hell, use both.
The trace (traceroute) is a tool which tells which networks a network packet would pass through to reach their IP address (from your IP address to them). It's useful when an ISP ignores you and then you go to the next one up in the queue (called going upstream) who'll be the people who supply bandwidth to them. That can result in small-ISP losing their account or whatever. The first few items in the traceroute are always the network you're at yourself obviously. All that said, since Level3 is essentially a major provider [a backbone] they provide services for ISPs themselves so going upstream isn't applicable.
There does need to be some evidence supplied e.g. email headers, links to messages and logs info or other evidence. I'm not sure what checking it against full headers of an e-mail from the suspected person (i.e. the x-originating IP item in the header) would do, since doesn't matter if it's who you think it is, you just want it stopped regardless. But it's definitely worth collating the evidence and submitting a complaint.
What
kappaloo said is technically often true
but their annoying posts may very well come under the AUP e.g. the Other Prohibited Activities section etc.
Whois:
OrgName: Level 3 Communications, Inc.
Address: 1025 Eldorado Blvd.
City: Broomfield
StateProv: CO
PostalCode: 80021
Country: US
NetRange: 4.0.0.0 - 4.255.255.255
CIDR: 4.0.0.0/8
NetHandle: NET-4-0-0-0-1
NetType: Direct Allocation
NameServer: NS1.LEVEL3.NET
NameServer: NS2.LEVEL3.NET
Updated: 2004-06-04
OrgAbuseHandle: APL8-ARIN
OrgAbuseName: Abuse POC LVLT
OrgAbuseEmail: abuse@level3.com