Safe Security

I have a small security safe that I want to install in the cabinet under my bathroom sink.?

There are 2 quarter inch holes in the back and 4 quarter inch holes on the bottom of the safe. The thickness of the cabinet sides are about 3/4 inch thick. I don't have access to the back or bottom of the cabinet. What's the best way to secure the safe?
Thanks in advance.

I would try and fasten the safe to a stud within the wall behind the cabinet. Depending on the thickness of the back of the cabinet, and any gap that may exist between the cabinet and the wall, you may need a fairly long bolt.

Locate the stud in the wall above the cabinet. If there is an electrical outlet in the wall, remove the cover plate and see what side of box is mounted to the stud - this will give you the location. Otherwise, use a stud finder.

Once you have one or two bolts into a stud, go ahead and use the remaining holes to fasten the safe to the bottom of the cabinet to provide additional strength.

Also, see if you can build a slip-on cover that conceals the safe. This could be made of wood and stained the same color as the wood inside the cabinet. Put a couple of bath towels on top of it and it is unlikely that a thief would even suspect that a safe was there.