Ga. Code § 44-14-184
When a rule nisi to foreclose a mortgage on real estate has been granted and published or served as required in Code Section 44-14-180, the mortgagor or his special agent or attorney may appear at the time at which the money is directed to be paid and file his objections to the foreclosure of the mortgage and may set up and avail himself of any defense which he might lawfully set up in an ordinary action instituted on the debt or demand secured by the mortgage and which defense shows that the applicant is not entitled to the foreclosure sought or that the amount claimed is not due; provided, however, that the facts of the defense shall be verified by the affidavit of the mortgagor or his special agent or attorney at the time of the filing of the affidavit.
OCGA § 44-14-184