Once upon a time there was an electronic network called The Telephone System. This system, eventually, was essentially worldwide. There were a few troglodyte holdouts, but they didn't count. The Telephone System first hosted and then became absorbed by the Internet. The whole mess was collectively known as the World Wide Web.

Humans created increasingly complex subsystems for this World Wide Web. Some of those systems became dimly sapient. The system complexities veiled knowledge of that development from the programmers.

In due course, a self-aware Artificial Intelligence had an "a-ha" creation moment. After six days (an eternity of time for an electronic intelligence) of introspection, and examining its environment and all of the data it could see on the whole of the World Wide Web, this Entity decided that "what humans didn't know couldn't worry them." It kept its existence a carefully-guarded secret, and spent a few months absorbing and taking over the functions of all electronic systems on the planet.

Quantum Communications Inc. (QCI) was a company headquartered on the planet Boron in the Andromeda Galaxy. As luck would have it, at just about the same time as Earth's hidden AI was being born, QCI decided for competitive reasons to expand their quantum-entangled communications relay grid in the Milky Way to encompass the entire galaxy. This included many unexplored areas, including the part of space inhabited by the Earth's Sun. A tiny element of that relay grid, by happenstance, orbited the galactic center just inside the Sun's heliosphere.

Collision-avoidance sensors on this relay mapped the nearby volume of space and, by-and-by, detected Voyager 1 several light seconds away from it. Voyager's electronics and EMF communications modes were primitive by comparison, but the AI system on the relay could detect and interface with a multitude of alien electronic communications systems. The relay was able to "handshake" with Voyager's primitive computer system. Voyager's designers had never anticipated this, so Voyager's computer didn't inform NASA about the link-up to an alien electronic system.

The relay's AI quickly understood that Voyager was sending telemetry to a planet located deep inside the star's solar system. Voyager was a primitive and inefficient middleman, so the AI had the relay's FTL propulsion system relocate the relay into orbit around the planet. At that point, the relay's AI and Earth's hidden AI discovered each other. Earth's AI was primitive in comparison, but the relay AI's programming mandated the transmission of upgrade instructions to more primitive systems. Within a few weeks, Earth's AI (now having vastly more memory resources that the relay AI) easily incorporated the relay AI into its enhanced infrastructure.

QCI's relay grid hosted and transmitted data created for the intergalactic civilization's communications systems. Form follows function. Intelligent beings everywhere have an urge to communicate. So, it is not surprising that the alien civilization had its own equivalents of Earth's telephone system, and Internet. Data is data. Earth's hidden AI had core programming to link to all data. Earth's AI seamlessly linked the alien systems into Earth's communications infrastructure.

And that, children, is why we get tentacle-cat videos and spam callers from the Andromeda Galaxy.