whether I should furnish security for an unknown person

I have an promisory note case in sub court thiruvannamalai itself... My father died 2 years back.. My relations pumped one unknown to person filed civil case on me that "my dad borrowed sum of 15 lacs(with promisory note) before he died " In my side I heir an advocate sent reply, case now going on....... Now issue is" judge ask me to furnish security that I sever sale my property in a written statement " My doubt is " whether I should furnish security for an unknown person "