I'm sure there are safeguards against such things, but this is something totally different that no one knew anything about. Plus when it was created, you can bet it was created with the ability to override such safeguards to ensure it's success. Anyone capable of creating such a program would have no issue hacking in.

@Taylorfirst1 said:

So Niska was able to just walk into some public establishment and upload new code to every synth in the world. And there are no safe guards of any kind to prevent someone from doing that? Did that seem a little to easy to anyone else?

I figured that since the code was written by that super genius synth creator guy, perhaps he had created a super hack to bypass the normal firewalls. I think the synths all get updates on a regular basis too, so there is a way for them to access changes. What surprised me, as it did Niska apparently, is that the changes did not happen for all synths all at once.