Small business users of Gmail, Yahoo! mail and Hotmail were vulnerable to corporate spies when logged into their accounts on public Wi-Fi networks, a penetration tester has found.
Business users of public Wi-Fi hotspots, such as those at cafes, who sent commercially sensitive information were at risk, said Hacklabs tester Chris Gatford.
Employees of small businesses often used free email services as their main business email accounts.
"By default, users of all three popular webmail services are completely vulnerable once logged in via public Wi-Fi," Gatford said.
Only Gmail had an option to always use HTTPS, a secure way to send information over the web but it had to be manually enabled making it likely most users were not protected.
Gatford demonstrated that the login process (usernames and passwords) was encrypted with secure socket layer (SSL). But once logged in over public Wi-Fi, documents and text in a default Gmail, Yahoo! or Hotmail account were transmitted in a way that someone with wireless sniffing tools such as Wireshark, Hamster or Ferret could easily intercept, he said.
Why do cloud webmail services not have SSL by default?
Soghoian said that webmail services had a strong incentive not to force SSL because "using and processing SSL transactions consumes vastly more processing power than regular transactions ... so providing users [full-time SSL] protection costs money".
Spokesmen for Yahoo!, Microsoft and Google told iTnews that their webmail login pages were secured with HTTPS and indicated they were "currently looking into" making it the default setting.
But several expressed concern that blanket implementation would result in a slow or unreliable user experience.
In a shot across the bows of Yahoo! and Microsoft, Google said "no other major webmail provider offers free, always-on HTTPS, and most don't provide any support for HTTPS at all".
Google said it "strives to provide a high level of security to our users" and "enables users to access a number of applications including Gmail, Docs and Calendar via HTTPS".
"Google Apps administrators also have the option to enforce HTTPS across an entire domain," the spokesman said
Yahoo! said it "takes online security seriously and take steps to safeguard user information".
"[We have] offered SSL and other password encryption methods for many years [and] rolled out SSL as our standard Web login approach across the Yahoo! network to deliver industry-standard encryption [but only for the login process]," a spokesman said.
"We are continuing to explore additional opportunities to embed SSL into the Yahoo! Network ... and recommend users read Safety Tips when Accessing Yahoo! Mail Using Public WiFi Spots."
A Microsoft spokesman said it offered encryption via SSL as an "option at log-in" and that "HTTPS is not necessarily a panacea ... other vectors need equal attention [so] we are investing in comprehensive solutions such as stronger credentials and protection against cookie replay attacks".
Microsoft encouraged Hotmail users to read its tips for protecting your privacy when using public WiFi.
How to secure your webmail
Gmail users should enable the setting to always use HTTPS.
Yahoo! and Hotmail users don't have this choice and should avoid sending any financial, private or commercially sensitive information using these accounts over Wi-Fi.
Gatford said anyone using a free webmail service for business should only ever access it in public over mobile broadband using 3G USB adaptors offered by Optus, Vodafone/Three or Telstra.
He said that information transmitted over these telecommunications networks was much more difficult to intercept and copy.