The IWF assesses child sexual abuse content according to the levels detailed in the Sentencing Guidelines Council's Definitive Guidelines of the Sexual Offences Act 2003 (PDF 369KB). Page109 'Part 6A: Indecent Photographs of Children' lists the levels for establishing the seriousness of child sexual abuse images as below:
Levels Description
1 Images depicting erotic posing with no sexual activity
2 Non-penetrative sexual activity between children or solo masturbation by a child
3 Non-penetrative sexual activity between adults and children
4 Penetrative sexual activity involving a child or children, or both children and adults
5 Sadism or penetration of or by an animal