Nasty links underneath post & plugins disappeared

Hi all,

I’ve got some troubles with my website. Underneath we got some nasty links with viagra and stuff. I want to delete those. I read it could be some code injection. What kind of code should I like for in my theme code?

Also all our plugins disappeared, could that be related?
Especially the SEO disappeared… Which is very painful since we had a good SEO proof website.

Thanks in advance!