millions of years old alien ship, which somehow awoke to the presence of my
brainwaves and established neural interface allowing me to control it more or
less.
This is good because it tells us two things that we are going to really need:
- the ship is capable of energy interaction at a distance (it has something akin to Culture's effectors).
- it is capable of very fast and accurate modelizations allowing it to "reverse engineer" mindstates of a mammal that didn't even exist when the ship was built.
Armed with those two capabilities, entering the Internet is a breeze.
Radio waves do not penetrate water unless they're very, very low frequency - that's why ELF are used to communicate with submarines. This is no obstacle to the ship, it will simply pick those waves from the surface, eleven watery kilometers above.
First of all, the ship analyzes the Internet traffic in the submarine cables - either SEA-US or AAG (Asia-America Gateway) landing in San Luis Obispo. The ship is easily able to decode the packet scheme and IPv4 addressing and routing (both are orders of magnitude simpler than brain signaling), and by observing the traffic it also discovers that this signaling is loss resistant. Lost packets will be retransmitted, and lost packets are not at all uncommon.
At that point, the ship assumes the identity of one of the less common transmitters - maybe a spare server in La Union, Philippines - and replaces some random packets from a common transmitter in Changi North, Singapore, with packets of its own. The transmitter assumes the packets were lost in transit and simply retransmits, not even bothering to warn anyone - this is all done by the lowest levels of the TCP/IP stack. If it was someone browsing an Internet page, would he notice that slightest of delays and do more than idly blaming the provider?
Now the ship is able to ping the Internet and elicit responses, allowing it to determine a truly unused IP public address among those that transmit from one side to the other of the AAG. Immediately after, it assumes that address and starts transmitting by hijacking other people's packets.
As far as the Internet is concerned, a valid system just powered up in Singapore, and the noise level on the line increased by less than 0.1%. Nothing to worry about.
(A Culture GCU such as the Grey Area would have simply rewritten the OS of some server and made it an extension of itself while idling in orbit around Alpha Centauri, acquiring a valid IP and all the bandwidth it might need, but let's assume this ship has a much shorter range).
As soon as an IP conflict arises (if it ever does!), the ship simply switches to another unused address.
With its technology, it is trivially capable of reading the binary code of any operating system on a remote computer, disassembling it and finding the requisite bugs and zero-day exploits, and take control. This way, it can infiltrate the Earth data systems and, for example, establish a fake identity and get assigned a small range of addresses - or even a top level domain of its own - paying with fake money appeared from nothing in some insufficiently protected bank server.
In its quest for information, after downloading Wikipedia, the ship would probably start posting on Stack Overflow under an assumed name. Hm. I can't really say I'm comfortable with where this is going...