Fake Amazon vouchers are being used to spread malware via Android mobiles. The attack sends an SMS message to all the contacts in a mobile phone offering a free Amazon voucher. If the recipient opens the message on an Android phone the malware tries to install itself and cycle is repeated.
Our advice is to delete any messages you’re unsure about and if your running an Android mobile make sure it’s got Anti-Virus software installed. Avast have a free product here if you’re unsure: https://www.avast.com/en-gb/free-mobile-security