IBM's stock price recorded its worst single-day performance in over 25 years on Monday, after artificial intelligence startup Anthropic announced that its Claude Code tool could assist in modernizing Cobol.
IBM's stock closed down 13.15% on Monday, at $223.35, marking the largest single-day drop since October 2000. With this decline, IBM's stock has fallen 27% in February, potentially setting the stage for the largest monthly drop since at least 1968.
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COBOL stands for Common Business-Oriented Language, a programming language that emerged in the late 1950s and has dominated the field of business data processing, widely used in scenarios such as payment processing and retail transaction systems. Anthropic stated that approximately 95% of ATM transactions in the U.S. use COBOL, making it a key area for AI disruption at a lower cost.
On Monday, Anthropic announced that Claude Code can automate the most complex exploratory and analytical tasks involved in the COBOL modernization process. Anthropic wrote in a blog post:
<blockquote>
&#34;In the past, modernizing Cobol systems often required a large number of consultants and took years to sort out workflows. Tools like Claude Code can automate the exploration and analysis phases, which account for the majority of the workload in the COBOL modernization process.&#34;
&#34;Every day, trillions of lines of COBOL code run in production environments, supporting critical systems for finance, aviation, and government. Nevertheless, the number of people who truly understand this language is decreasing year by year.&#34;
&#34;AI excels at simplifying tasks that have historically made COBOL modernization costs prohibitively high.&#34;
</blockquote>
Most of the mainframes running Cobol are manufactured by IBM. Media reports indicate that this round of sell-off has made IBM the latest company to face heavy pressure due to concerns that AI will dampen the growth prospects of traditional enterprises.
A significant portion of IBM's revenue is still related to its mainframe business. These large servers, owned by clients, run applications based on Cobol. Cobol is a language that predates the mainstream programming languages of today's tech industry. Mainframes continue to be favored by clients with strict requirements for high reliability, such as financial institutions or government departments.
Anthropic stated that Claude Code can help modernize COBOL codebases by mapping dependencies between thousands of lines of code, documenting workflows, and identifying potential risks. These tasks &#34;could take months to uncover if done by human analysts.&#34;
The blog post points out:
<blockquote>
&#34;Traditional code modernization has stagnated for years because the cost of understanding old code often exceeds the cost of rewriting it. Artificial intelligence has changed this calculation.&#34;
</blockquote>
<h2>Cybersecurity Concept Stocks Plummet Again</h2>
This year, software stocks have performed poorly overall due to market concerns about the disruptive risks posed by artificial intelligence.
Last Friday, Anthropic launched a new security feature for its Claude AI model called Claude Code Security, triggering widespread sell-offs in cybersecurity stocks. Anthropic stated that this feature can scan for security vulnerabilities in codebases and identify software flaws for human review.
On Monday, cybersecurity concept stocks fell for the second consecutive trading day. CrowdStrike and Zscaler both dropped about 10%, while Netskope fell more than 12%. SailPoint declined by 9.4%, and Okta, SentinelOne, and Fortinet all saw declines of over 4%. Palo Alto Networks fell by 3%, while Cloudflare, which recently benefited from the Moltbot craze, plummeted by 9.6%. The iShares Cybersecurity and Tech ETF dropped by 4.65%, and the Global X Cybersecurity ETF fell to its lowest level since November 2023.
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The massive sell-off is attributed to new artificial intelligence tools launched by companies such as Anthropic, OpenAI, and Alphabet. Investors are concerned that the &#34;vibe code&#34; capability—using artificial intelligence to write software code—will enable users to create applications on their own, thereby weakening demand for traditional products and putting pressure on corporate growth, profit margins, and pricing power.
Evercore ISI analyst Amit Daryanani wrote:
<blockquote>
&#34;We understand why the market might view the migration of large mainframes as a potential negative for IBM, but we want to point out that IBM has already provided customers with various modernization options. Our judgment is that customers could have chosen to migrate from mainframes, but they still choose to stay on this platform.&#34;
</blockquote>
In fact, services that make Cobol easier to use are not new—many large tech companies have launched similar products. IBM itself released a tool in 2023 that uses artificial intelligence to handle Cobol, including updating Cobol to the more popular and modern programming language Java.
IBM CEO Arvind Krishna stated in July 2025 that IBM's AI coding assistant for mainframes &#34;has seen very broad adoption.&#34; He mentioned that in most cases, customers use the tool to understand their Cobol codebases and decide which parts need modernization

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Anthropic stated that its Claude Code tool can automate the transformation of traditional systems running COBOL. IBM's stock price plummeted 13.15% on Monday, marking the largest single-day drop since 2000, with a cumulative decline of 27% in February. Meanwhile, after the release of the new AI security feature Claude Code Security, the cybersecurity sector suffered a significant setback for the second consecutive trading day, with stocks like CrowdStrike and Zscaler experiencing sharp declines, and the iShares Cybersecurity and Tech ETF falling by 4.65%

- IBM's stock experienced its worst single-day performance in over 25 years, dropping 13.15% after Anthropic introduced its Claude Code tool for modernizing COBOL.  
- The decline reflects a significant monthly loss of 27% in February, raising concerns about traditional companies' growth prospects amid AI advancements.  
- Anthropic's tool aims to simplify the modernization of COBOL, which is still prevalent in key sectors, while the cybersecurity sector also faced a downturn due to market fears of AI disruption.

Anthropic continues to shake the market: IBM plummets 13%, marking the largest drop in 25 years, cybersecurity stocks face another heavy decline