Type Internet worm
Creator Bob Thomas
Date Discovered 1971.03.16?
Place of Origin Cambridge, Massachusetts, USA?
Source Language Assembly
Platform Tenex
File Type(s)
Infection Length
Reported Costs

Creeper was one of the first programs that resembled an Internet worm. It ran on the old Tenex operating system and moved through the ARPANET, a predecessor of the current Internet. Creeper caused infected systems to print the message "I'M THE CREEPER : CATCH ME IF YOU CAN.". Not only was Creeper the first rogue mobile program, but another version of it was created that could be considered the first worm, as it would spread, leaving copies of itself. Yet another similar program was created to fight the Creeper infections, named Reaper, which was the first nematode.


The Creeper program would start to print a file, but then stop, find another Tenex system, open a connection, pick itself up and transfer to the other machine (along with its external state, files, etc.), and then start running on the new machine. The program rarely if ever actually replicated itself, rather it "jumped" from one system to another. Infected systems printed the text "I'M THE CREEPER : CATCH ME IF YOU CAN.".


It is uncertain how much damage Creeper actually caused. Some sources claim that Creeper replicated so many times that it crowded out other programs. The extent of the damage is unspecified. Most sources say the worm was little more than an annoyance.


A version of Creeper was allegedly created by Ray Tomlinson that could replicate itself. Another program called "Reaper" was created to delete Creeper. It is presumably similar in most if not every way, except that it looks for a Creeper infection and deletes it. Reaper is considered the first antivirus program.

Other Facts

In addition to having the first worm in history, Tenex is the OS which saw the first email programs, SNDMSG and READMAIL, in addition to the use of the "@" symbol on email addresses. The first email program, email message and email itself were invented by Ray Tomlinson, the creator of the replicating Creeper. Bob Thomas and Ray Tomlinson were employees of Bolt, Beranek and Newman (now known as BBN Technologies), which developed these and many other early Internet programs and protocols. BBN itself was purchased by Raytheon, a defense contractor that has produced missiles as well as surveillance technologies for social networks, including the RIOT, or Rapid Information Overlay Technology.

As Creeper's run through the DARPANET was ages ago, a complete description of this program may require some real Internet archeology (actually visiting places where these things happened to find information). The information is horribly incomplete, its accuracy is uncertain and sources often conflict on some details. No samples or source codes are currently available for study.

Although it is technically a violation of the Virus Encyclopedia's policy forbidding viral/worm sources or binaries to be posted to any page here, Creeper and the OS that it ran on are so old that there is next to no harm in them being posted here. If you have Creeper in binary or source form, please do not hesitate to upload it to this Wiki, as that would be greatly appreciated. As for any safety concerns, we will assume that anyone still running a TENEX machine from circa 1970 is intelligent and experienced enough to protect his/her computer.


Most sources claim Creeper ran through the DARPANET in the early 1970's, but David Sims's article in Wired says it was in the late 1960's. Some articles are a bit more exact, but they are no more consistent.

Whether or not the worm even existed is a source of debate. There is a claim that the person sending the messages was a disgruntled employee who managed to hack the network to send the messages in order to harass the admins. Other people found out and began doing the same thing.

Sources History of Malware, 1970s

Thomas M. Chen. Department of Electrical Engineering SMU, The Evolution of Viruses and Worms (PDF) (broken link. Not captured by

Alexander Dewdney. Scientific American, (1984, v.250, N 5, pp. 15-19) In the game called Core War hostile programs engage in a battle of bits

John Metcalf., Creeper and Reaper

John Shoch, Jon Hupp Communications of the ACM (1982.03 Volume 25 Number 3, pp.172-180) The "Worm" Programs - Early Experience with a Distributed Computation

Ray Tomlinson. Email Home.

Dave Crocker. Living Internet, "Email History".

Corinne Cullen Hawkins. A Software Bestiary: Computer Parasites & Remedies

Ed Skoudis, Lenny Zeltser. Malware: Fighting Malicious Code, "A History of Worms". Prentice Hall, 2003.11.07. O'Reilly Safari Online Books.

Sean Kazen. E-Articles, A Brief History of Worms

David Sims. Wired, Privacy's Yin and Yang 2000.07.21

PR Newswire. Raytheon Completes Acquisition of BBN Technologies. 2009.10.26

Joseph L. Flatley. Engadget, Creeper, the first computer virus, is 40 years young today. 2011.05.17

Ryan Gallagher. The Guardian, Software that tracks people on social media created by defence firm. 2013.02.10

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