Someone creates porn site back links to my site

One of my cites was hit by negative seo by unknown person. They are creating anchor text back links to my site from spam sites including those of porn sites and sites which sell Viagra and sex toys!!!
Those anchor texts are my primary keywords. The anchor text links are positioned in the design of that sites, ie near the contact us, about us stuffs.
What legal action i can take against them?
Is there any way to delete those links other than disavow ?

See original post by JithinC