under what conditions does the behavior occur?
- any visitor? ie any stranger coming in is attacked.
- specific age or gender of visitor? Ex. small children, or men.
- specific visitor behavior, ie reaching out to touch the cat.
How often does it occur? Hourly, daily, weekly, monthly, etc
How long does the behavior last? Once and run? Continues until visitor leaves or cat runs away?
Are there specific locations where the scratching occurs such as where the cat sleeps, or near a food bowl or litterbox?
Are the custodian and/or person being scratched aware of cat body language, such as flattened ears and tail twitching may indicate agitation (fear or aggression)?
With more details, it may be possible to develop a plan for managing the behavior and possibly to extinguish it. I'd be happy to help brainstorm one with more information. PM if you'd like.
It may be helpful to review some of the content on the website and/or pick up some of the books from Pamela Johnson-Bennett of
Cat Behavior Associates I've found her material to be quite good. Many topics are covered on the website and in the books.