My car does not have the key fob.  How can I turn off the security system?  The dash board security idiot light keeps flashing when the car is parked.  I'm more worried about the battery drain of the dash flashing light, then the car being stolen.  

The LED flashing probably drains the battery less than the battery's own internal resistance- no real affect on charge life.

Is it flashing rapidly or once every few seconds?

 

Those LEDs use less energy to blink for a week than the dome lights use when you open the door for 30 seconds.

rapidly.

^^^ what they said, minimal battery drain - for LONG storage, I guess just pull the neg batt. terminal to stop all dark current. But for a week or 2, maybe a month - leave it.

 

you can get fobs from ebay. I forget, but one type of flashing is 'valet' mode.

Rapid flashing means the alarm is in valet mode and will not arm, per cars101.com.

 

 

5. Valet mode or alarm off: alarm light (red dot center dashboard display) rapidly flashing 3 times means the alarm is in "Valet" mode and is not setable. The light will stop flashing when you start the car. 
To set valet mode or just to disable the security alarm system: 1. unlock all doors 2. physically open the driver's door 3. hold the UNLOCK button on remote for 2+ seconds or so. The red 'security' light will then flash 2 times a second until the car is turned on.

http://www.cars101.com/subaru/keyless.html#alpine