Case Library / Phishing / 0ktapus: mass SMS-phishing of Okta credentials hits Twilio, Cloudflare, Mailchimp and 130+ orgs
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0ktapus: mass SMS-phishing of Okta credentials hits Twilio, Cloudflare, Mailchimp and 130+ orgs

A single SMS-phishing campaign lured employees to fake Okta login pages, harvested ~9,931 credentials and 5,441 MFA codes across 136 organizations, and used the access to pivot into downstream supply-chain attacks.

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Reviewed by the Social Engineering Examples team.

What Happened

Beginning in at least March 2022, attackers ran a large-scale text-message (smishing) phishing campaign against employees of companies that use Okta for single sign-on. Employees received SMS messages impersonating their IT department, warning that a password had expired or a schedule had changed and linking to a lookalike Okta login page. Victims who entered their username, password, and MFA/one-time code delivered them to the attackers. Group-IB, which uncovered the operation while investigating an incident for a client, codenamed it "0ktapus" and detected 169 unique phishing domains. Group-IB's analysis of the attackers' data showed roughly 9,931 stolen user credentials (about 3,120 with corporate emails and 6,811 without) and 5,441 captured MFA codes, spanning 136 identified victim organizations, most of them U.S.-based IT, software, and cloud companies. Confirmed breaches included Twilio (detected Aug 4, 2022; ultimately 163 customers and 93 Authy accounts affected) and Mailchimp and Klaviyo; Cloudflare was targeted on July 20, 2022, when 76 employees were texted and three entered credentials, but hardware security keys prevented any compromise. The stolen access was used to launch downstream supply-chain attacks: Twilio access exposed data enabling re-registration attempts on ~1,900 Signal accounts, and a Mailchimp compromise touched DigitalOcean's transactional email.

How the Attack Worked

The campaign paired smishing with a real-time adversary-in-the-middle relay. Attackers registered domains containing keywords like "okta," "sso," "vpn," "mfa," and "help" plus the target's brand, and cloned the organization's exact Okta login page so it looked identical to what employees expected. SMS was chosen because texts feel personal and urgent and bypass email security gateways; messages spoofed the internal IT team and used time pressure. Crucially, when a victim submitted credentials, the phishing kit relayed them instantly to the attackers (via a Telegram channel), who entered them into the real login portal; the fake page then prompted for the one-time MFA code, which was likewise relayed and used before it expired, defeating SMS/TOTP-based MFA. In some flows the page also pushed AnyDesk remote-access software. It worked because the lures exploited routine IT-driven behavior, the pages were pixel-accurate, freshly registered domains evaded brand-monitoring detection (Cloudflare's spoofed domain was registered under 40 minutes before the blast), and phishable one-time codes gave a false sense of protection.

The Lure & the Tell

Lure: a text message appearing to come from your company's IT/help desk saying your password expired or your work schedule changed, with a link to an "Okta"/"SSO" login page. Tells: the message arrives by SMS (legitimate IT rarely texts urgent login links), it creates time pressure, and the link goes to a domain that only looks official (e.g., brand-okta.com, brand-sso.net) rather than your real Okta/SSO URL. Any page asking you to re-enter both your password and your MFA code after clicking an unsolicited link is a red flag.

Outcome

Group-IB publicly disclosed the campaign on August 25, 2022, linking the Twilio and Cloudflare incidents to one operation and publishing infrastructure indicators. Twilio revoked compromised accounts, engaged forensics, notified 163 affected customers and 93 Authy users, and worked with carriers, registrars, and hosting providers to take down infrastructure. Cloudflare was not breached because FIDO2 hardware keys with origin binding blocked the attackers even after credentials were phished. The episode became a landmark case for why SMS/TOTP MFA is phishable and why phishing-resistant hardware keys matter.

Why It Matters

0ktapus showed that low-sophistication tooling (a simple phishing kit plus SMS) could compromise well-known, security-mature companies at scale by defeating MFA through real-time relay of one-time codes. It demonstrated the supply-chain blast radius of identity compromise: breaching one vendor (Twilio, Mailchimp) opened paths into their customers (Signal, DigitalOcean). The clearest lesson is that not all MFA is equal. Cloudflare's phishing-resistant FIDO2 keys stopped the exact attack that breached peers relying on push/OTP codes.

Defenses

Deploy phishing-resistant MFA (FIDO2/WebAuthn hardware security keys with origin binding) instead of SMS or TOTP one-time codes. Train employees that IT will not text urgent login links, and give an easy way to report suspicious messages. Verify the exact SSO/Okta domain before entering credentials, and treat links from unknown sources as suspicious. Use secure web gateways / DNS filtering to block newly registered and lookalike domains, and monitor for brand-impersonation domain registrations. Enforce endpoint controls that block unsanctioned remote-access tools (e.g., AnyDesk). Rotate credentials and terminate active sessions immediately on suspected compromise, and require MFA re-enrollment.

Sources
Attack Chain & Defense
The sequence the attacker ran
How it could have been stopped
1
Reconnaissance and target list-building: The operation is documented (per Twilio's own incident report and the CISA/FBI advisory AA23-320A on the related Scattered Spider ecosystem) as compiling employee names and personal mobile phone numbers, in some cases including family members, likely drawn from data brokers, prior breach dumps, or OSINT such as LinkedIn and corporate directories, to make bulk SMS lures land convincingly.
Countering Stage 1: Employee and family personal phone numbers scattered across data brokers and breach dumps are largely outside a company's direct control; the realistic control sits downstream, training staff to distrust unsolicited "IT" texts no matter how the attacker got the number, and watching for bulk lookalike-domain registrations against the brand.
2
Infrastructure setup: Attackers registered lookalike domains pairing the target company's brand with identity-provider keywords such as "okta," "sso," "vpn," "mfa," and "help" through low-friction registrars, and built a phishing kit that cloned the victim's exact Okta/SSO login page, hosted on commodity cloud infrastructure; Group-IB catalogued 169 such domains.
Countering Stage 2: Monitor domain registrars and certificate-transparency logs for newly registered lookalike domains combining the company brand with SSO-related keywords, and use secure web gateway or DNS filtering that flags or blocks very recently registered domains by default.
3
Mass SMS lure delivery: Attackers sent bulk smishing texts spoofed as internal IT or help desk, using urgency themes like password expiration or a schedule change, and rotated across phone numbers and carriers to stay ahead of blocking.
Countering Stage 3: Give employees a fast, low-friction way to report suspicious texts to a security team, and train staff that legitimate IT will not send urgent, unsolicited login links by SMS.
4
Credential harvesting via cloned login page: Employees who clicked through landed on the pixel-accurate fake Okta page and entered their username and password, believing it was their real employer SSO portal.
Countering Stage 4: Verify the exact SSO/Okta domain before entering credentials, and rely on enterprise browser or password-manager controls that refuse to auto-fill credentials on a domain that doesn't match the saved legitimate URL.
5
Real-time adversary-in-the-middle relay of MFA codes: The phishing kit relayed captured credentials instantly, via a Telegram channel, to the attacker, who logged into the real portal and triggered a genuine one-time code; the fake page then re-prompted the victim for that code, relayed it in turn, and the attacker used it before expiry, defeating SMS and TOTP-based MFA.
Countering Stage 5: Deploy phishing-resistant MFA (FIDO2/WebAuthn hardware security keys with origin binding) instead of SMS or TOTP codes. Cloudflare showed this is the one control that stops this exact relay technique even after credentials are already phished.
6
Optional remote-access payload: In some flows, once a victim had submitted both credentials and MFA code, the phishing page pushed the AnyDesk remote-access tool, which would have given attackers direct control of the victim's machine had it been installed; Cloudflare's Cloudforce One team documented this fallback step.
Countering Stage 6: Enforce endpoint controls and application allowlisting that block installation of unsanctioned remote-access software such as AnyDesk.
7
Access, data theft, and downstream pivot: With valid sessions or credentials, attackers reached internal and customer-support systems (as at Twilio and Mailchimp), harvested customer data, and used that vendor-side access to attempt account takeovers at the vendors' own customers, such as re-registration attempts on Signal accounts and password-reset attempts on DigitalOcean accounts, completing the objective of broad, monetizable access across a supply chain.
Countering Stage 7: Apply least-privilege access to customer-support tooling, monitor for anomalous internal system access, and rotate credentials and terminate sessions immediately on suspected compromise, so a vendor breach cannot silently cascade into its customers' accounts.
Quick Facts
Victim
130+ organizations including Twilio, Cloudflare (attempt, not breached), Mailchimp, and Klaviyo; downstream victims included Signal, DigitalOcean, and Twilio's Authy users.
Location
Primarily United States (114 of 136 identified victim orgs U.S.-based or with U.S. staff); also Canada and other regions
Date
March 2022 to August 2022 (Group-IB disclosure August 25, 2022; Twilio breach detected August 4, 2022; Cloudflare attempt July 20, 2022)
Impact
No consolidated dollar figure publicly disclosed; impact measured in credential/data theft (~9,931 credentials, 5,441 MFA codes), 163 affected Twilio customers, 93 compromised Authy accounts, and 1,900 Signal phone numbers exposed.
Status
Confirmed
Case Type
Real-World Incident
Sector
Financial Services & Insurance, Retail & E-commerce, Technology & Software, Telecommunications
Threat Actor
Organized Crime
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