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4 Steps and Cost Estimates to Identify Posters on 5chan (Japanese Internet Forum)


4 Steps and Cost Estimates to Identify Posters on 5chan (Japanese Internet Forum)

“5ch,” the largest anonymous bulletin board site in Japan, is a hub of diverse information. However, it can also be a platform for defamation against individuals and companies. If a post that could be considered defamatory is made, how can the poster be identified? We will explain the methods for identifying the poster and provide an estimate of the legal fees required for this process.

What is “5channel (formerly 2channel)”?

Features and Management of 5channel (formerly 2channel)

5channel is the largest anonymous bulletin board site. The current operator is an overseas corporation, “Loki Technology Inc”.

Interestingly, the once famous anonymous bulletin board site “2channel” no longer exists. “2channel”, which was established by Hiroyuki Nishimura in 1999, split into two sites in 2014 due to a dispute over management rights. The former “2channel” changed its site name and domain to “5channel”, and the operator was replaced by someone other than Mr. Nishimura. Meanwhile, Mr. Nishimura separately established a new “2channel (”.

The circumstances and relationships surrounding the emergence of “5channel (formerly 2channel)” and “2channel (” are complex, so they are explained in a separate article.[ja]

Examples of Defamation on 5channel (formerly 2channel)

5channel (formerly 2channel) has threads that gather the latest news, posts about various companies and celebrities, and bulletin boards where these are collected. Therefore, there are posts such as:

  • Posts about arrest articles that were once reported and have already disappeared from official sites such as newspapers
  • Posts about companies being “black companies”

As mentioned later, in order to identify the poster, it is necessary for the post to be illegal. Posts that cannot be considered illegal cannot be identified. Therefore, whether or not the problematic post is illegal is an important point when considering identifying the poster.[ja][ja]

Step 1 in Identifying the Poster: Requesting IP Address Disclosure

What is an IP Address?

The first step in identifying the poster on 5channel (formerly 2channel) is to request the disclosure of the IP address. An IP address is a unique identifier that each device connected to the Internet has, it can be likened to an “address on the Internet”.

5channel (formerly 2channel) allows anonymous posting. While information such as “name” and “E-mail (email address)” is required when creating a thread or replying to an existing thread, it is acceptable to leave these fields blank, and in practice, most posts are made anonymously.

Therefore, the operators of 5channel (formerly 2channel) do not even know the names, let alone the addresses, of the posters. Instead, 5channel (formerly 2channel) does record the IP addresses of those who post, so it is necessary to initiate a procedure to disclose these logs.

Requesting the Disclosure of the Poster’s IP Address through Provisional Disposition Procedures

In order to disclose the IP address, it is generally necessary to use court procedures.[ja]

This court procedure is specifically a provisional disposition, which is a swift procedure. While trials can take a considerable amount of time, provisional dispositions can be implemented in about 1-2 months. The average attorney’s fees for this procedure are said to be

about 300,000 yen for the retainer fee, and about 300,000 yen for the success fee

What are the attorney’s fees and compensation flow for reputational damage? [ja]

It should be noted that in this procedure, it is possible to request both the disclosure of the IP address and the deletion of the post at the same time. The above fees are for both procedures. However, the cost will naturally vary depending on the content and volume of the posts in question. In the case of 5channel (formerly 2channel), there are many cases where a large number of defamatory posts are made against a particular individual or company, and in such cases, the cost can inevitably increase.

Also, since the operator of 5channel (formerly 2channel) is a foreign corporation, there will be slightly higher actual expenses, such as the cost of obtaining the corporation’s registration.

Need to Assert and Prove that the Post is Illegal

In order to have the court recognize the disclosure (and deletion) of the IP address in this procedure, it is necessary to assert and prove that the post is illegal. This may be a bit confusing, but what is required here is strictly “that the post is illegal”. When requesting deletion not through court procedures but through a deletion request, the reasons for requesting deletion can be broadly divided into

  • Violation of terms of use
  • Illegality

For example, 5channel (formerly 2channel) has a deletion judgment standard that

Information that poses a realistic danger of causing harm to society, such as methods of making bombs, information suggesting drug trafficking

How to request deletion of posts on 5channel (formerly 2channel)[ja]

is subject to deletion. However, this is strictly a decision by the operator of 5channel (formerly 2channel) to voluntarily delete such posts, and it does not necessarily mean that such posts are “illegal”.

In order to have the request for IP address disclosure recognized, you need

  • A legal argument that the post is illegal
  • Evidence to support this

Why the specific post can be considered illegal, and what kind of evidence should be prepared, is precisely the know-how and expertise of a lawyer specializing in reputational damage measures.

Step 2 in Identifying the Poster: Prohibition of Log Deletion

Once the IP address is disclosed in Step 1, the provider used by the poster (such as Nifty for fixed-line connections, or Docomo for mobile connections) becomes clear. The provider keeps a log of the name and address of the subscriber who was using the IP address at the specific date and time. Therefore, the next step is to request the provider to disclose the name and address… However, providers do not keep logs indefinitely. In particular, mobile operators delete connection logs after about three months. For fixed-line connections, it’s about 6-12 months.

Therefore, the principle is that a new court procedure is needed to issue an order to the provider to “prohibit the deletion of the log”.

However, in reality, many providers, if notified that “we are about to request the disclosure of the name and address through the court, so please keep the log without deleting it for a while”, will often preserve the log. Therefore, it can be said that in many cases, this part can be covered by notification alone. However, even in this situation, it is necessary to argue and prove how the 5channel (formerly 2channel) post in question is illegal.

There is not much information on the internet about the average attorney’s fees for this notification, but it is believed that in many cases, about 100,000 yen is sufficient.

Step 3 in Identifying the Poster: Request for Disclosure of Name and Address

If the provider has preserved the log in Step 2, the next step is to request the provider to disclose the poster’s name and address. This part is not a quick provisional disposition, but a formal court procedure. The name and address are, of course, significant personal information. For example, even if someone posts on 5chan (formerly 2chan) that a certain company is a “black company”, if there is sufficient evidence for the post, the post may not be illegal, and the poster’s personal information should perhaps be protected. The court, with this issue in mind, only allows the disclosure of the name and address if it is recognized as illegal in a formal procedure.

The average attorney’s fee for this part, according to information on the internet, is

about 300,000 yen for the retainer fee, and about 200,000 yen for the success fee

What are the attorney’s fees and compensation flow for reputational damage?[ja]

It can be said that this also depends on the content and quantity of the post.

Step 4 in Identifying the Poster: Claim for Damages

If you win the lawsuit in Step 3, the name and address of the poster (more precisely, the subscriber of the line used by the poster) who posted on 5channel (formerly 2channel) will be disclosed. You will then claim for damages from this poster, including the attorney’s fees (investigation costs) incurred in Steps 1-3, and compensation for emotional distress.

Under this system, if you successfully identify the poster, your claim for damages is accepted, and the amount of damages is compensated, there will be no financial burden on the victim’s side. However, there is a risk whether you can identify the poster and, even if you can, whether you can recover the damages. We explain these in detail in the article below.[ja]

However, in relation to the risk of not being able to identify the poster, 5channel (formerly 2channel) blocks IP addresses and providers that are known for “trolling”. These are highly anonymous lines, such as overseas proxy servers and public wireless LANs.

Also, in the case of companies, access to 5channel (formerly 2channel) from within the company is often prohibited as it is considered access to non-work-related sites.

Therefore, it can be said that 5channel (formerly 2channel) is a site where there are fewer posts from highly anonymous lines and company lines compared to the general theory of the Internet, and there are many posts from home and personal mobile phone lines.


As such, identifying the poster who made an anonymous post on 5chan (formerly 2chan) is by no means easy, but it is not impossible either. In fact, if left unattended, the post may remain for a long time, which could lead to reputational risk.

Given the complexity of the actual post deletion process, it is necessary to consult with a lawyer who is well-versed in practical matters. For specific information on how much it will cost and how long it will take to delete a post, it would be a good idea to consult at least once.

Managing Attorney: Toki Kawase

The Editor in Chief: Managing Attorney: Toki Kawase

An expert in IT-related legal affairs in Japan who established MONOLITH LAW OFFICE and serves as its managing attorney. Formerly an IT engineer, he has been involved in the management of IT companies. Served as legal counsel to more than 100 companies, ranging from top-tier organizations to seed-stage Startups.

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