As other answers have indicated, "insecure" is a much more common word than "unsecure". (The word "unsecured" has an intermediate frequency, but its meaning doesn't seem consistent with what you want.)
The most common nouns that occur after "unsecure" do seem relevant to your desired usage, however: the Ngram Viewer indicates that they are things like "unsecure network(s)", "unsecure line", "unsecure environment", "unsecure connection", and "unsecure channel".
The word "insecure", when used attributively before a noun, is actually often used with non-human nouns, but the top ones shown by Google are abstract like "insecure position", "insecure footing", "insecure basis", "insecure foundation(s)". So if we chose a random occurence of the word "insecure", it probably won't be related to information security. But this by no means indicates that it would be incorrect to speak of insecure devices.
In fact, because "insecure" is so much more frequent than "unsecure", the phrase "insecure network(s)" still seems to be much more common than "unsecure network"; likewise, "insecure channel" and "insecure connection" appear to be more common than "unsecure network" and "unsecure connection".
I would say it looks like you could use either word with this meaning.