I think it is Korean or Chinese.

It keeps popping up on my Firefox browser before crashing the entire thing needing the machine to be reset. I have no idea when it could have happened, but since Christmas my internet has been buggered and this has now appeared maybe six times in one hour.

Not Korean. It's either Chinese or it is Japanese Kanji

Give me a few mins.

EDIT: I tried few OCR sites, like http://www.newocr.com/ but the image is too small to get the correct results.

You can try google translate handwriting if you have the patience, or wait for someone to translate it here.

Be careful around those Asian porn sites. They're worse than the Russian ones.

I don't understand Kanji but... I'd bet for a spyware \ virus.
Better scan the computer asap

It's either Chinese or Japanese, I see no Hiragana, so it's hard for me to say. Not good enough to recognize any of it.

Korean looks like this:
Hangul:
[url=http://en.wikipedia.org/wiki/Hangul#mediaviewer/File:Chosungul_or_Hangul_logo_%28New_Type%29_at_%28Black_Design%29.svg]http://en.wikipedia.org/wiki/Hangul#mediaviewer/File:Chosungul_or_Hangul_logo_%28New_Type%29_at_%28Black_Design%29.svg[/url]
Hanja:
[url=http://en.wikipedia.org/wiki/Hanja#mediaviewer/File:Hanja.png]http://en.wikipedia.org/wiki/Hanja#mediaviewer/File:Hanja.png[/url]

Bearing in mind I speak tiny, little amounts of it and can read none, but from what I remember Koreans don't use Hanja a lot, and they're pretty much Chinese anyway. There may be differences, but I am unaware of them.
Edit, again: The Hanja are pretty much Chinese, not necessarily the people... not that they're not similar, but... I'll just shut up now.

"Be sure to drink your Ovaltine"

Imagine if it said, "What does this fox say?". Ai-ai-ai-ai-ai!

Wa-pa-pa-pa-pa-pa-pow!

I wish this had happened on the machine I use to watch porn - I just formatted that one last weekend.
Nope this is the machine I use for downloading games and other internet usage.

I have currently let AVG and Malware Bites both run checks and both came back with nothing. Onto internet checking.

That's chinese. It's says something about "stopping cover (as in frontpage I think)" if I got it well.

YOU NINJA BASTARD! :P

Don't know if this is accurate or helps:

https://support.mozilla.org/en-US/questions/1035523

The relevant bits say:

no worries, it's nothing malicious, but it is caused by this one addon which appears to have compatibility issues with firefox 34...

That joke took 9 hours to soak in before I got it. But now I can't stop laughing. That's goddamn funny. I tip my Christmas candy cane hat to you, sir.

That's chinese and as far as I can tell it's all gibberish.