In order to identify and remove these when you suspect something is wrong or just to ensure your system is safe before engaging in online banking or shopping you can run a free Online Antivirus Scan provided by one of the major antivirus vendors.

• Bitdefender QuickScan 
• compatible with Microsoft Internet Exporer, Mozilla Firefox and Google Chrome
• small plugin size
• fast results - the scan takes 60 seconds or less
• does not provide disinfection, for removal of viruses you must scan using Bitdefender Online Scanner

• Trend Micro HouseCall
• identifies and fixes a wide range of threats including viruses, worms, Trojans, and spyware
• custom scan options allow users to specify which folders to scan
• quick scan option offers targeted scanning of critical system areas and active threats, reducing scan times to within a few minutes.
• stand-alone, browser-independent implementation eliminates compatibility issues associated with browser-activated scanners.
• Smart Scan technology refers to patterns in the cloud, delivering the latest protection while reducing download times. 
• Smart Feedback shares threat information with the Smart Protection Network, which correlates data from a global intelligence network to quickly discover new threats. 
• review and restore lets you check and compare scan results and recover files.
• enhanced detection and cleanup addresses rootkits and other sophisticated threats.

• ESET Online Scanner
• compatible with Microsoft Internet Exporer, Mozilla Firefox and Opera
• detects both known and unknown forms of malware, such as viruses, worms, Trojans, phishing and spyware.
• uses the same ThreatSense® technology and signatures as ESET Smart Security/ESET NOD32 Antivirus
• provides disinfection of detected items