NEW DELHI: Big Brother is watching. With the Central Monitoring System (CMS) at home and PRISM from the US, millions of users worldwide have become vulnerable to online surveillance by state agencies without even realizing it. No surprise, several cyber security experts feel that building one's own personal firewall is a good way of fortifying online privacy One enterprising netizen has compiled a list of services, from social networks to email clients, and even web browsers, that offer better protection from surveillance. They are listed on a web page called prism-break.org.When asked about steps that a digital native can take to protect his privacy and online data, Sunil Abraham, executive director of Bangalore-based non-profit Center for Internet and Society said, "Stop using proprietary software, shift to free/open source software for your operating system and applications on your computer and phone. Android is not sufficiently free; shift to CyanogenMod. Encrypt all sensitive Internet traffic and email using software like TOR and GNU Privacy Guard. Use community based infrastructure such as Open Street Maps and Wikipedia. Opt for alternatives to mainstream services. For example, replace Google Search with DuckDuckGo."Use of licensed or proprietary software, which bind users legally when it comes to use and distribution, seems to be losing favour among an informed niche. While alternative software cannot offer absolute protection, it is being seen as a "better-than-nothing" option. Anonymisers like TOR, though also not entirely foolproof, are also a popular option among those who wish to keep their web usage untraceable. Once installed on a browser, anonymisers can hide the route that digital traffic takes when sent from your computer over a network before emerging at an end node.There is one caveat, though. Some websites can deny service to users operating on certain anonymising networks. Also, anonymisers are known to reduce browsing speeds. In India, where broadband speeds are already abysmally low, anything that slows one down even further would find popularity hard to come by.Computer and network security expert Aseem Jakhar too recommends open source software since they offer the convenience of customization to suit one's encryption needs and are able to verify the source code. For laypersons, there are other tools. "One can use anonymisers like TOR which encrypt your communication and hide your identity. With these it becomes very difficult to exactly locate the source. For email clients, it is best to use ones that offer end-to-end strong encryption," he says. Jakhar, co-founder of open security community "null", also recommends the use of customized and Linux systems for more advanced users. Default Linux distributions, he points out, may have free online services which can again be analysed by the governments.The home-bred CMS programme seeks to directly procure data pertaining to call records and internet usage for intelligence purposes without going through telecom service providers. There were fears of abuse when information about the programme, kept under strict wraps by the government, trickled in. Department of Telecom and Ministry of IT and Communication have been reticent about the state of implementation of the 400-crore rupees programme.PRISM, a similar, international monitoring programme mounted by the US and revealed to the world by the US National Security Authority whistleblower Edward Snowden , has raised concerns of safeguarding digital information the world over.