Social engineering exploits vulnerabilities at different layers (i.e. technical, social layer) in an organizational defense structure. It is therefore important to understand how to defend against these attacks using a holistic defense approach including multiple countermeasures. The literature suggests a plethora of countermeasures, little research has however been done to assess their effectiveness in managing social engineering threats. In this paper we attempt to obtain a deeper understanding of how to defend against a type of social engineering attack that attempts to install malware on computers through e-mail or portable media. We explore commonly proposed countermeasures needed to prevent this type of attack, and if any dependencies between them exist. Through a combined method approach of surveying the literature and conducting semi-structured interviews with domain experts we identified a set of countermeasures that provide empirical input for future studies but could potentially also give organizations guidance on how to manage social engineering-based malware installation attacks.