Running an unsupported management tool introduces risk. If you must keep ASDM 7.18 online:
For administrators with a valid service contract, the most direct method is Cisco Software Central. Navigate to the Cisco Software Download page. Search for . Select Version 7.18(x) from the list.
If you are planning for the future, consider migrating to Firepower Management Center (FMC) for FTD devices. However, for existing ASA deployments, ASDM 7.18 remains a reliable workhorse.
Expected output: "Device Manager image file, disk0:/asdm-7181.bin"
Once downloaded, upload the .bin file to your ASA's flash memory via TFTP, FTP, or SCP. Then, configure the ASA to use the new image: