The valid disadvantage of using a software firewall versus a hardware firewall is:
A malware infection on the machine could compromise the software firewall processes.
This is true because a software firewall runs on the host machine, making it susceptible to being affected by malware or other security breaches that target the operating system. In contrast, a hardware firewall operates independently of user devices and can provide a layer of security that isn't directly impacted by malware on those devices.