Cloudflare turns away a blocklist-clean VPS address at ChatGPT's front page

The post's author runs an IP reputation tool ^[16] and says the two kinds of check answer two different questions. Spam blocklists answer "has this address sent spam," the author wrote. The risk system Cloudflare runs for OpenAI answers "does this address look like a machine in a datacenter, and what has it been used for." ^[14]

The sample only measures the first question. Addresses came from /24 blocks that each provider's ASN announces in BGP, and the origin ASN was checked for each one ^[1]. The seed is fixed at 20260928, and all 360 records are published under CC BY 4.0 ^[1]. The checks were reverse DNS, eight DNS blocklists, RDAP and BGP origin ^[2]. The 47 list hits fell on 47 listed addresses, so each listed address appeared on exactly one list ^[1]. RackNerd had 25 of them, one in each of 25 different /24 blocks ^[6]. That means 25 of its 30 sampled addresses were listed, about 83% ^[2]. The author concluded that "a hit here tells you about the list's coverage of the ASN, not about the specific box you would be renting." ^[7] The other eleven providers together had 22 listed addresses out of 330, or 6.7% ^[3].

DMIT shows the same spread from one block to the next. It had 3 listed addresses out of 30, one each in three unrelated /24s, and the /24 holding the author's server came back clean ^[15]. The sample even drew a neighbour from that block, 154.21.82.51, with no listings and a DMIT reverse DNS name ^[8].

The residential flag weakens the datacenter explanation. The author describes Cloudflare's question as whether an address looks like a datacenter machine ^[14]. Yet the author's own tool said this address was not a datacenter ^[9]. A datacenter flag from that classifier would not have predicted the block. The post does not show which signals Cloudflare used. "There is no blocklist query that would have predicted this, because the risk engine is not running a blocklist query," the author wrote ^[13].

That conclusion rests on one address ^[2]. One counterexample is enough to break the rule that a clean reputation means a working connection. It cannot say how often the block happens at DMIT, at RackNerd, or within any single /24 ^[2].

I think teams running agents or scripted access to ChatGPT from a cloud host should take a reputation score as a statement about spam history. They should plan separately for a Cloudflare block ^[4]. The check that caught this one is the last one the author ran: a plain GET from the address itself, done before the box is committed to the job ^[4]. It is also the cheapest check in the post, at one HTTP request ^[4].