ESET Mobile Security is one of many pieces of software vended by ESET a leading security company in both the desktop and mobile worlds. Businesses in particular benefit from ESET's commitment to publishing information publicly and informing other vendors about new threats but anyone can benefit from the discounts they provide when covering multiple devices. Mobile Security as the name implies focuses on tackling threats unique to mobile devices: tracking and locking lost devices and filtering out spam for example.
Of Course It's Still An Antivirus Too
The antivirus core in ESET Mobile Security is comparable in technology to ESET's other antiviruses. Thus it doesn't use up too much processing power (or battery life) and it finds threats fairly effectively but it takes a while. More important is that ESET Mobile Security tackles spam: it removes spam notifications and screens calls and texts. And if your device gets lost it can be locked.
What You Need
If malware is a significant worry for you it might be wise to find a dedicated mobile antivirus like what Norton offers. ESET Mobile Security does much better against subtler threats than just viruses: it helps ameliorate physical theft of your device it efficiently sweeps spam out of your notifications and it screens out a lot of other smaller threats all without causing problems for you. In that it is fantastic not simply as an antivirus but for improving your mobile security.