It's called a CRYPTO LOCKER virus and if you get it, it locks up all your files and they can only be unlocked by paying for a code from the virus people.
It's lately attached to emails from Australia Post, saying you have a parcel to collect,
or from the Federal Police claiming you have a fine.
Before you click any links, read the email address it's actually from and ask yourself how would they know my email address to send me this message.
Even if you are expecting a parcel, the people you've ordered from wouldn't pass your email address to Australia Post.
Be careful people, be aware of who is sending you emails.