Researchers conducted a series of tests on popular 3G/4G mobile modems (data dongles) and routers discovered an impressive number of serious flaws. The SCADA Strangelove team tested devices from various vendors, such as Huawei (two different modems and a router), Gemtek (a modem and router), Quanta (two modems) and ZTE (one modem) The results are disconcerting, a significant number of vulnerabilities were found in this equipment: Huawei modems with the most recent firmware updates are the ones with a better layer of security.”]
Source: http://securityaffairs.co/wordpress/42472/hacking/3g4g-modems-flaws.html