E-mails relayed through the South African Internet Exchange (SAIX), that have not reached their intended destination, may have been rejected as spam.
One of SAIX eight servers was blacklisted by the Spam and Open-Relay Blocking System (Sorbs) on 17 August.
Sorbs, a real-time blacklist (RTB) which lists servers that have been reported to send out spam, is used by many companies as a spam-filtering service. Before receiving an e-mail, servers that have been subscribed to the service check if the relaying server has been blacklisted, and if the response is positive, it rejects the e-mail.
Telkom, of which SAIX is its wholesale Internet division, says SAIX detected the listing on 18 August when it became public. Telkom spokesperson Lulu Letlape says the offending user was traced and various blocks were applied to prevent this user from creating further problems.
Business as usual
Being blacklisted by Sorbs is a normal part of the business of providing Internet services, says Mike Kuczmierczyk, Sentech's product manager for value-added services. Recently, Sentech was also blacklisted by Sorbs, but has now been delisted.
An unnamed source, however, disagrees with Kuczmierczyk. Receiving a warning from Sorbs is normal, but prompt action by the ISP will ensure the matter never reaches the blacklisting stage. The source alleges SAIX was not vigilant, and the blacklisting should not have lasted this long.
"In addition to users' e-mail being rejected as spam, local companies that subscribe to Sorbs may also be forced to switch their Sorbs spam filter off to allow SAIX-relayed e-mails to get through," he says.
If they don't allow the e-mails to get through, their business operations may be disrupted, he notes. The price of switching off the Sorbs spam filter, however, is that real spam will also filter through, he says.
Taking action
"SAIX takes exception to users causing RBL listings of a SAIX server's IP address and we demand a suspension of the account with immediate effect to prevent further problems," Letlape says. "ISPs are required to provide feedback within 24 hours."
Kuczmierczyk, however, notes that Internet subscribers may be unaware that they are sending out spam as a result of a virus attack. As a result, Sentech first sends a friendly warning before suspending the account.
MyADSL founder Muller says the situation in SA was complicated because Telkom only offered dynamic IP addresses. This allowed rogue Internet users to spam, knowing full well that the IP address would be assigned to someone else the following day, he says.
Under the ADSL regulations promulgated last week, ADSL providers must provide static IP addresses, he notes.
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