किस प्रकार का सॉफ़्टवेयर कंप्यूटर सिस्टम पर विज्ञापन दिखाकर अपने डेवलपर के लिए स्वचालित रूप से राजस्व उत्पन्न करता है, जो अक्सर 'पे पर क्लिक' तंत्र का उपयोग करता है?

In which phase of its lifecycle does a computer virus place an identical copy of itself into other programs or system areas on the disk?

Consider the following security statements: I. Polymorphic viruses can change their code to avoid detection. II. Stealth viruses hide the infection from antivirus software. III. Multipartite viruses attack both boot records and executable files. IV. Ransomware cannot affect network drives. Which of the statements given above are true?