It is a perfectly human reaction to be annoyed if malware infects your smartphone or laptop.

But just how extraterrestrials might respond is harder to predict.

An accidental cyber attack launched against aliens who might be hundreds of thousands of years more advanced than us is just one problem bothering British scientists working on a message to send ET.

The small team from the 20-strong UK Seti (Search for Extra-Terrestrial Intelligence) group is bidding for a one million dollar (£650,000) prize on offer for the best method of saying "hello" to our galactic neighbours.

Russian internet billionaire Yuri Milner put up the prize as part of a huge new investment in Seti, which has the backing of leading scientists.

Seti generally involves listening out for alien signals using powerful radio telescopes and computer software that can scan thousands of frequencies.

But some experts believe we should also be shouting out our presence to the cosmos by beaming messages to targeted stars.

Dr Anders Sandberg, a UK Seti member from the Future of Humanity Institute at Oxford University, said it was important to ensure that we stream "clean" digital signals that do not cause unintentional offence.

Speaking at the British Science Festival, taking place at the University of Bradford, he said: "There are complications about using a complicated language or syntax for sending a message - I've written a paper about this.

"A too complex language can hide an awful lot of weird stuff, which is a real problem for our own computer security. Sending out a message that could hide malware might be something the aliens don't like."

So far UK Seti has not made a great deal of progress on its message. In fact it is not entirely sure one should be sent at all. A vote taken at a recent meeting was split 50/50 between those in favour and those against.

The argument against calling ET is that it might attract the wrong kind of attention. Top physicist Professor Stephen Hawking is one of those urging caution and is quoted as saying: "If aliens visit us, the outcome would be much as when Columbus landed in America, which didn't turn out well for the Native Americans."

Dr Sandberg said he hoped a consensus would eventually be reached. Meanwhile, UK Seti has set up a four-man alien message working group.

Opinion is also split about what kind of content should be included in a radio broadcast to aliens.

"Pictures are iconic and easy to interpret," said Dr Sandberg. "On the other hand you have the school that says, no, we don't know whether the aliens have eyes. Pictures might be totally the wrong thing to send to them. That school would say let's use something universal like mathematics."

Whatever kind of message is sent, it most definitely should not be sexist, according to Dr Jill Stuart from the London School of Economics.

She said an example of a "wrong" message was the pictorial representation of humans carried on the Voyager 1, the probe launched in 1977 that is now heading out of the Solar System.

It shows a hand-waving man standing in front of a "passive" woman.

"I wouldn't want to impose a narrative that has a specific gender approach," said Dr Stuart, also speaking at the science festival. "You might say what would the aliens care about gender? But it's also forcing us to look in. Part of the exercise is looking at our collective humanity and deciding what's important to us."