The abs light is permanently on for past 6 months,though brakes working fine.about a month ago,brake fluid has slow leak and pperiodically red brake light appears but disappears as soon as you refill.source of leak not identified,just small drops found under car when it has been parked for a while

Master Cylinder is leaking past its seals. As for abs, could be related or separate issue.

If the caliper is not defective, it could be the rubber flex hose going to the caliper.

could be leak from master cylinder this should be evident by fluid running down between master and booster or leaking from piston seal on caliper, caliper will dip fluid onto wheel rim or road leaving a visual mess easy to see

Take it to a shop which has a lift, like an oil change or muffler shop, have them put on the lift. The leak will be apparent as it will be a wet recent stain. Then you will know if you are looking at a brake line fix, a leaking master or slave cylinder.

Do not blame the guy who did the pads 10 months ago, anything he did wrong would be immediately apparent and would not take 8 months to show.

sounds as if there might be a brake fluid leak somewhere in the system.check the master cylinder to see if the brake fluid is low or almost empty,if the fluid is up then it could be a master cylinder that has an internal leak(meaning the fluid is leaking past the internal seals but not leaking out of the cylinder).it also can be a problem with the abs hydraulic control module leaking.you should have the abs system checked for any codes in that system which may help find the problem quicker,if you don`t find any problem with the other suggestions

I think these lights are not related. The ABS light means the ABS is not working, and has nothing to do with the brakes working. You can have brakes and not have the ABS part working. I don't think a bad ABS would turn on the check engine light, but it may.

Check the volume of fluid in the master cylinder reservoir. Low fluid would account for an intermittent brake light.
Check to be certain you are not leaking any fluid.
Noises may be from many causes.
Did you "bed" the pads & rotors?

Look for wires hanging, near the tire area under the car. An ABS sensor wire may be broken or the sensor is damaged.
Getting the system scanned will tell you exactly what is going on.

The red brake light is the key here. That usually indicateds a hydraulic problem. Check you fluid level in master cylinder and see if it is low. Also the level indicator sensor there in the master cylinder maybe sticking or corrioded. If ABS sees the red brake light it will shut off and turn on the ABS light,also traction control would be disabled as well.

If you have not replaced any brake lines or brake calipers, then It sounds like that the brake proportioning valve or the brake master cylinder if defective. If the the brake pedal goes to the floor, the master cylinder is at fault. If not, the proportion valve, which is part of the ABS valve body is defective. Have your local garage check these two components for possible problems.