Cybersecurity-related stocks surged following the disclosure of a major information leak at the end of September and expanding ransomware damage in October. The article examines 20 stocks, including 8 frontrunners that hit their daily limit-up, based on the latest earnings and investor relations information.
The trigger was a series of disclosures of major information leaks beginning at the end of September. Disclosures followed one after another concerning the leakage of member information from the Times Car car-sharing service and Yakiniku King, as well as the possibility of an information leak at Daiwa Securities. In October, IDC Frontier’s cloud service suffered a ransomware attack, suspending services for approximately 500 companies and local governments. The National Police Agency reported 123 ransomware incidents in the first half of 2026, while the enactment of the Active Cyber Defense Act and the launch of operations under standards for critical infrastructure also coincided with these events.
The market reaction was dramatic, with a succession of related stocks hitting their daily limit-up from 6 October onward. On the 8th, 16 stocks hit their daily limit-up, increasing the weight of cybersecurity-related stocks. Cyber Security Cloud rose from ¥1,973 on 2 October to ¥4,105 on the 13th, nearly doubling in a short period, while ZenmuTech also briefly hit its daily limit-down.
This article is structured around a detailed examination of 20 stocks based on the latest earnings and investor relations information: 8 “frontrunners” that led the limit-up rush, 4 “second-wave” stocks in the midst of their price movements, and 8 “laggards and strong performers” that could become the next market leaders. It organizes the characteristics and earnings trends of each stock and presents information to support stock selection.
Chapter 1 covers Cyber Security Cloud as a frontrunner and a leading domestic cloud-based WAF provider, outlining its business, revenue composition, ARR trends, recent initiatives and risk factors. It also summarizes key points on Broadband Security, which provides auditing, assessment and monitoring as an integrated service, including its revenue composition, current-year plan, projected contribution from G-MDR, and the scale of its customer base and related risk factors.