A telnet service responds to a plain port scan. So it was categorically not hidden. Vodaphone explain this themselves in the linked register article:

>It added the Telnet service was found during an audit, which means it can't have been that secret or hidden: "The issues were identified by independent security testing, initiated by Vodafone as part of our routine security measures, and fixed at the time by Huawei.

>I think this article is disingenuous.

Is 'The Register'. Being disingenuous is their bread and butter when you tune out the comedic writing style. I used to follow their climate change reporting as an interesting counterpoint as they were biased towards trying to disprove it. These days they more or less ignore climate change as a topic compared to five or ten years ago, if you look at frequency of articles.

I won't deny it's bad, but it's more of a smoking crater than a smoking gun. A genuine vulnerability existed, and it wasn't swiftly remove (apparently due to it being crucial to their manufacturing operations). Notwithstanding the potential for this to be an underhandedly engineered backdoor, there doesn't seem to be any evidence of it being more than an oversight similar to others common in the industry.