During a routine software update at Horizon Solutions, a mid-sized IT firm in Raleigh, North Carolina, an employee downloads a file utility from a popular third-party site to streamline document processing. During the installation, the user is prompted to install an optional "productivity toolbar" and a "system optimization tool," which are bundled with vague descriptions. Shortly after, the employee notices intermittent pop-up ads, an altered browser homepage, and sluggish PC performance, though network logs also show occasional unexplained data transfers during off-hours. A security scan flags the additional programs as potentially harmful, but a deeper analysis reveals no immediate file encryption or self-replicating code.
What type of threat are these unwanted programs most likely classified as?