The exploit - a tool that makes attacking a vulnerability easier - was posted to the Bugtraq security e-mail list on Wednesday. Its existence "makes the possibility of a worm that targets these (systems) more likely", said Friedrichs.
The vulnerability, announced Monday by Internet Security Systems and then expanded upon by the Apache Software Foundation, could allow an attacker to take control of an affected Web server.
A flaw in the way Apache handles uploads could allow an attacker to send a specially formed request to the server and cause it to deny service to legitimate users or take the system over, both groups said.
Almost two-thirds of the world's Web servers use Apache, according to data from Web server monitoring firm Netcraft.
CERT/CC (Computer Emergency Response Team/Co-ordination Centre), a US government-funded computer security body located at the Carnegie Mellon University, and Internet Security Systems both updated their advisories on the vulnerability after the release of the exploit, urging users to patch their systems.
Despite the presence of an exploit, SecurityFocus has not "seen increased attack activity" focused at Apache systems, Friedrichs said.
SecurityFocus monitors the networks of over 9,000 companies in more than 145 countries for security data and then aggregates it to create a picture of global, regional and industry-specific Internet security.
Friedrichs said there is usually a one to two-week period between vulnerability announcements and attacks.
Though the exploit released on Wednesday only attacks Apache installations running on the OpenBSD operating system, "it's not a monumental task for someone to modify it (to work with other operating systems)", he said.
Users should patch their systems immediately and check with their vendors for more information, Friedrichs said.
"People should be making the patching of their Apache servers a high priority," he said.