The long-running feud between the makers of the Bagle and Netsky Windows viruses seems to be losing its venom.
The clash prompted the virus writers to pump out new versions and at the last count there were now 21 variants of Bagle and 20 of Netsky circulating.
Anti-virus firms said the makers of the malicious programs had worked hard to find new tricks for variants to use.
Despite the rash of variants neither is close to the number of different versions racked up by the Agobot virus.
The first version of Bagle appeared on 28 January and the original Netsky mass-mailing virus was spotted on 16 February.
Until early March the makers of these Windows viruses were happy to send out occasional variants of the original program.
But comments included in the Bagle.J variant revealed growing antipathy between the two groups of virus creators.
The feud apparently blew up because the creators of the Bagle virus were jealous of the media attention that Netsky was getting.
The bad blood was marked by a rapid increase in the numbers of new variants. On 3 March several variants of the viruses were released at the same time.
Since then novel variants have continued to be released. Bagle.U and Netsky.T are the latest incarnations.
The groups behind the two viruses have varied the tricks they use to make people open their creations and infect their PC.
For instance the attachments arriving with some Bagle variants took the form of password protected archives or zip files. The password to unlock the attachment was included in the body of the infected e-mail.
To stop anti-virus software grabbing the passwords to unlock the attachments, Bagle.O and N use a picture of the password rather than plain text.
But now, said Carole Theriault, security consultant at Sophos, the feud appears to be cooling off.
"The last Netsky we saw was on the 22nd of the month," she said, "and it's been a few weeks since we were seeing one every other day."
She said that if the feud goes on Netsky and Bagle could become one of the few viruses to rack up more than 26 variants. In such a case, she said, the variants will be named using two letters rather than one.
Currently the virus with the most variants is called Agobot and there are more than 170 versions of that created since it first appeared in October 2002. BBC News