There's no doubt that we have a lot of computer security issues on our planet right now. Ransomware seems to be a daily issue, with new variants constantly being released; hardware issues in CPUs give bad guys the ability to steal your data; and lax security in the "Internet of Things" (IoT) enables bad guys to run denial of service attacks against the biggest companies in the world. However these may be simple annoyances compared to what extraterrestrials could do to our planet's IT infrastructure.
In a paper written by Michael Hippke and John G. Learned, the researchers explain various ways an alien civilization could destroy the world, either intentionally or unintentionally, by embedding code in a message. They speculate that even simple markup languages like TeX and LaTeX could be used maliciously, and highlight the difficulty in decoding the languages manually. In addition, the paper details that an alien AI could begin a negotiation with humanity, in essence social engineering an attack.
One recommended solution is to build a "prison" on the moon, a computer that is used to decode alien messages, but is isolated from other networks and which could be remotely destroyed if necessary. However they go on to say that, "[c]urrent research indicates that even well designed boxes are useless, and a sufficiently intelligent AI will be able to persuade or trick its human keepers into releasing it." While there are no silver bullets to this problem, and the researchers note that the overall risk to humanity is low, it's a topic that can be fun to think about.
This topic is hardly new as there have been many books and movies that explore the concept of malicious invaders. For example, in the movie Species, the SETI project received a transmission with details on how to splice alien DNA with human DNA and the result was mayhem. What other interesting books, movies, and TV shows have you seen that address this topic?